Description of problem:
When SyncLunsInfoForBlockStorageDomainCommand calls to GetDeviceList and detects that there's a new LUN in the storage that is a part of the storage domain, or that there's an update for an existing LUN that is a part of the storage domain, it tries to update the DB.
However, if the storage domain contains a shared disk between two VMs, an exception is thrown and the storage domain is not synchronized (the DB is not updated).

Version-Release number of selected component (if applicable):
9bb30a5c970c79ca58c26625f0999417ea2bf05d

How reproducible:
100%

Steps to Reproduce:
Basically, this corner case happens when the LUN in the storage has a property that we need to update in the DB. For example, its size.
Here's one way to reproduce it:
1. Have a block storage domain with a shared disk between two VMs.
2. Take it down to maintenance.
3. Update the luns table in the DB so that at least one of the storage domain's LUNs will have a wrong size.
This query sets the size to be 0 for all the storage domains' LUNs:
UPDATE luns SET device_size = 0 WHERE volume_group_id = '<sd_vg_id>';
In my env, the LUNs with the following IDs were updated - 3514f0c5a51600489, 3514f0c5a5160048a.
4. Activate the storage domain.

Actual results:
2017-11-29 08:52:10,524+02 ERROR [org.ovirt.engine.core.bll.storage.domain.SyncLunsInfoForBlockStorageDomainCommand] (EE-ManagedThreadFactory-engine-Thread-50) [7a674124] Command 'org.ovirt.engine.core.bll.storage.domain.SyncLunsInfoForBlockStorageDomainCommand' failed: Failed managing transaction
2017-11-29 08:52:10,525+02 ERROR [org.ovirt.engine.core.bll.storage.domain.SyncLunsInfoForBlockStorageDomainCommand] (EE-ManagedThreadFactory-engine-Thread-50) [7a674124] Exception: java.lang.RuntimeException: Failed managing transaction
	at org.ovirt.engine.core.utils.transaction.TransactionSupport.executeInNewTransaction(TransactionSupport.java:224) [utils.jar:]
	at org.ovirt.engine.core.bll.storage.domain.SyncLunsInfoForBlockStorageDomainCommand.executeCommand(SyncLunsInfoForBlockStorageDomainCommand.java:86) [bll.jar:]
	at org.ovirt.engine.core.bll.CommandBase.executeWithoutTransaction(CommandBase.java:1205) [bll.jar:]
	at org.ovirt.engine.core.bll.CommandBase.executeActionInTransactionScope(CommandBase.java:1345) [bll.jar:]
	at org.ovirt.engine.core.bll.CommandBase.runInTransaction(CommandBase.java:1987) [bll.jar:]
	at org.ovirt.engine.core.utils.transaction.TransactionSupport.executeInSuppressed(TransactionSupport.java:164) [utils.jar:]
	at org.ovirt.engine.core.utils.transaction.TransactionSupport.executeInScope(TransactionSupport.java:103) [utils.jar:]
	at org.ovirt.engine.core.bll.CommandBase.execute(CommandBase.java:1405) [bll.jar:]
	at org.ovirt.engine.core.bll.CommandBase.executeAction(CommandBase.java:412) [bll.jar:]
	at org.ovirt.engine.core.bll.executor.DefaultBackendActionExecutor.execute(DefaultBackendActionExecutor.java:13) [bll.jar:]
	at org.ovirt.engine.core.bll.Backend.runAction(Backend.java:509) [bll.jar:]
	at org.ovirt.engine.core.bll.Backend.runActionImpl(Backend.java:491) [bll.jar:]
	at org.ovirt.engine.core.bll.Backend.runInternalAction(Backend.java:434) [bll.jar:]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) [rt.jar:1.8.0_151]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) [rt.jar:1.8.0_151]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) [rt.jar:1.8.0_151]
	at java.lang.reflect.Method.invoke(Method.java:498) [rt.jar:1.8.0_151]
	at org.jboss.as.ee.component.ManagedReferenceMethodInterceptor.processInvocation(ManagedReferenceMethodInterceptor.java:52)
	at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:422)
	at org.jboss.invocation.InterceptorContext$Invocation.proceed(InterceptorContext.java:509)
	at org.jboss.as.weld.interceptors.Jsr299BindingsInterceptor.delegateInterception(Jsr299BindingsInterceptor.java:78)
	at org.jboss.as.weld.interceptors.Jsr299BindingsInterceptor.doMethodInterception(Jsr299BindingsInterceptor.java:88)
	at org.jboss.as.weld.interceptors.Jsr299BindingsInterceptor.processInvocation(Jsr299BindingsInterceptor.java:101)
	at org.jboss.as.ee.component.interceptors.UserInterceptorFactory$1.processInvocation(UserInterceptorFactory.java:63)
	at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:422)
	at org.jboss.as.ejb3.component.invocationmetrics.ExecutionTimeInterceptor.processInvocation(ExecutionTimeInterceptor.java:43) [wildfly-ejb3-11.0.0.Final.jar:11.0.0.Final]
	at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:422)
	at org.jboss.as.ee.concurrent.ConcurrentContextInterceptor.processInvocation(ConcurrentContextInterceptor.java:45) [wildfly-ee-11.0.0.Final.jar:11.0.0.Final]
	at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:422)
	at org.jboss.invocation.InitialInterceptor.processInvocation(InitialInterceptor.java:40)
	at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:422)
	at org.jboss.invocation.ChainedInterceptor.processInvocation(ChainedInterceptor.java:53)
	at org.jboss.as.ee.component.interceptors.ComponentDispatcherInterceptor.processInvocation(ComponentDispatcherInterceptor.java:52)
	at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:422)
	at org.jboss.as.ejb3.component.singleton.SingletonComponentInstanceAssociationInterceptor.processInvocation(SingletonComponentInstanceAssociationInterceptor.java:53) [wildfly-ejb3-11.0.0.Final.jar:11.0.0.Final]
	at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:422)
	at org.jboss.as.ejb3.tx.CMTTxInterceptor.invokeInNoTx(CMTTxInterceptor.java:264) [wildfly-ejb3-11.0.0.Final.jar:11.0.0.Final]
	at org.jboss.as.ejb3.tx.CMTTxInterceptor.supports(CMTTxInterceptor.java:379) [wildfly-ejb3-11.0.0.Final.jar:11.0.0.Final]
	at org.jboss.as.ejb3.tx.CMTTxInterceptor.processInvocation(CMTTxInterceptor.java:244) [wildfly-ejb3-11.0.0.Final.jar:11.0.0.Final]
	at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:422)
	at org.jboss.invocation.InterceptorContext$Invocation.proceed(InterceptorContext.java:509)
	at org.jboss.weld.ejb.AbstractEJBRequestScopeActivationInterceptor.aroundInvoke(AbstractEJBRequestScopeActivationInterceptor.java:73) [weld-core-impl-2.4.3.Final.jar:2.4.3.Final]
	at org.jboss.as.weld.ejb.EjbRequestScopeActivationInterceptor.processInvocation(EjbRequestScopeActivationInterceptor.java:89)
	at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:422)
	at org.jboss.as.ejb3.component.interceptors.CurrentInvocationContextInterceptor.processInvocation(CurrentInvocationContextInterceptor.java:41) [wildfly-ejb3-11.0.0.Final.jar:11.0.0.Final]
	at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:422)
	at org.jboss.as.ejb3.component.invocationmetrics.WaitTimeInterceptor.processInvocation(WaitTimeInterceptor.java:47) [wildfly-ejb3-11.0.0.Final.jar:11.0.0.Final]
	at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:422)
	at org.jboss.as.ejb3.security.SecurityContextInterceptor.processInvocation(SecurityContextInterceptor.java:100) [wildfly-ejb3-11.0.0.Final.jar:11.0.0.Final]
	at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:422)
	at org.jboss.as.ejb3.deployment.processors.StartupAwaitInterceptor.processInvocation(StartupAwaitInterceptor.java:22) [wildfly-ejb3-11.0.0.Final.jar:11.0.0.Final]
	at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:422)
	at org.jboss.as.ejb3.component.interceptors.ShutDownInterceptorFactory$1.processInvocation(ShutDownInterceptorFactory.java:64) [wildfly-ejb3-11.0.0.Final.jar:11.0.0.Final]
	at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:422)
	at org.jboss.as.ejb3.component.interceptors.LoggingInterceptor.processInvocation(LoggingInterceptor.java:67) [wildfly-ejb3-11.0.0.Final.jar:11.0.0.Final]
	at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:422)
	at org.jboss.as.ee.component.NamespaceContextInterceptor.processInvocation(NamespaceContextInterceptor.java:50)
	at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:422)
	at org.jboss.invocation.ContextClassLoaderInterceptor.processInvocation(ContextClassLoaderInterceptor.java:60)
	at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:422)
	at org.jboss.invocation.InterceptorContext.run(InterceptorContext.java:438)
	at org.wildfly.security.manager.WildFlySecurityManager.doChecked(WildFlySecurityManager.java:609)
	at org.jboss.invocation.AccessCheckingInterceptor.processInvocation(AccessCheckingInterceptor.java:57)
	at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:422)
	at org.jboss.invocation.ChainedInterceptor.processInvocation(ChainedInterceptor.java:53)
	at org.jboss.as.ee.component.ViewService$View.invoke(ViewService.java:198)
	at org.jboss.as.ee.component.ViewDescription$1.processInvocation(ViewDescription.java:185)
	at org.jboss.as.ee.component.ProxyInvocationHandler.invoke(ProxyInvocationHandler.java:81)
	at org.ovirt.engine.core.bll.interfaces.BackendInternal$$$view2.runInternalAction(Unknown Source) [bll.jar:]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) [rt.jar:1.8.0_151]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) [rt.jar:1.8.0_151]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) [rt.jar:1.8.0_151]
	at java.lang.reflect.Method.invoke(Method.java:498) [rt.jar:1.8.0_151]
	at org.jboss.weld.util.reflection.Reflections.invokeAndUnwrap(Reflections.java:433) [weld-core-impl-2.4.3.Final.jar:2.4.3.Final]
	at org.jboss.weld.bean.proxy.EnterpriseBeanProxyMethodHandler.invoke(EnterpriseBeanProxyMethodHandler.java:127) [weld-core-impl-2.4.3.Final.jar:2.4.3.Final]
	at org.jboss.weld.bean.proxy.EnterpriseTargetBeanInstance.invoke(EnterpriseTargetBeanInstance.java:56) [weld-core-impl-2.4.3.Final.jar:2.4.3.Final]
	at org.jboss.weld.bean.proxy.InjectionPointPropagatingEnterpriseTargetBeanInstance.invoke(InjectionPointPropagatingEnterpriseTargetBeanInstance.java:67) [weld-core-impl-2.4.3.Final.jar:2.4.3.Final]
	at org.jboss.weld.bean.proxy.ProxyMethodHandler.invoke(ProxyMethodHandler.java:100) [weld-core-impl-2.4.3.Final.jar:2.4.3.Final]
	at org.ovirt.engine.core.bll.BackendCommandObjectsHandler$BackendInternal$BackendLocal$2049259618$Proxy$_$$_Weld$EnterpriseProxy$.runInternalAction(Unknown Source) [bll.jar:]
	at org.ovirt.engine.core.bll.storage.connection.ISCSIStorageHelper.syncDomainInfo(ISCSIStorageHelper.java:311) [bll.jar:]
	at org.ovirt.engine.core.bll.storage.domain.ActivateStorageDomainCommand.syncStorageDomainInfo(ActivateStorageDomainCommand.java:86) [bll.jar:]
	at org.ovirt.engine.core.bll.storage.domain.ActivateStorageDomainCommand.executeCommand(ActivateStorageDomainCommand.java:115) [bll.jar:]
	at org.ovirt.engine.core.bll.CommandBase.executeWithoutTransaction(CommandBase.java:1205) [bll.jar:]
	at org.ovirt.engine.core.bll.CommandBase.executeActionInTransactionScope(CommandBase.java:1345) [bll.jar:]
	at org.ovirt.engine.core.bll.CommandBase.runInTransaction(CommandBase.java:1987) [bll.jar:]
	at org.ovirt.engine.core.utils.transaction.TransactionSupport.executeInSuppressed(TransactionSupport.java:164) [utils.jar:]
	at org.ovirt.engine.core.utils.transaction.TransactionSupport.executeInScope(TransactionSupport.java:103) [utils.jar:]
	at org.ovirt.engine.core.bll.CommandBase.execute(CommandBase.java:1405) [bll.jar:]
	at org.ovirt.engine.core.bll.CommandBase.executeAction(CommandBase.java:412) [bll.jar:]
	at org.ovirt.engine.core.bll.PrevalidatingMultipleActionsRunner.executeValidatedCommand(PrevalidatingMultipleActionsRunner.java:204) [bll.jar:]
	at org.ovirt.engine.core.bll.PrevalidatingMultipleActionsRunner.runCommands(PrevalidatingMultipleActionsRunner.java:176) [bll.jar:]
	at org.ovirt.engine.core.bll.PrevalidatingMultipleActionsRunner.lambda$invokeCommands$3(PrevalidatingMultipleActionsRunner.java:182) [bll.jar:]
	at org.ovirt.engine.core.utils.threadpool.ThreadPoolUtil$InternalWrapperRunnable.run(ThreadPoolUtil.java:96) [utils.jar:]
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [rt.jar:1.8.0_151]
	at java.util.concurrent.FutureTask.run(FutureTask.java:266) [rt.jar:1.8.0_151]
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [rt.jar:1.8.0_151]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [rt.jar:1.8.0_151]
	at java.lang.Thread.run(Thread.java:748) [rt.jar:1.8.0_151]
	at org.glassfish.enterprise.concurrent.ManagedThreadFactoryImpl$ManagedThread.run(ManagedThreadFactoryImpl.java:250) [javax.enterprise.concurrent-1.0.jar:]
	at org.jboss.as.ee.concurrent.service.ElytronManagedThreadFactory$ElytronManagedThread.run(ElytronManagedThreadFactory.java:78)
Caused by: java.lang.IllegalStateException: Duplicate key org.ovirt.engine.core.common.businessentities.storage.DiskVmElement@410a2573
	at java.util.stream.Collectors.lambda$throwingMerger$0(Collectors.java:133) [rt.jar:1.8.0_151]
	at java.util.HashMap.merge(HashMap.java:1254) [rt.jar:1.8.0_151]
	at java.util.stream.Collectors.lambda$toMap$58(Collectors.java:1320) [rt.jar:1.8.0_151]
	at java.util.stream.ReduceOps$3ReducingSink.accept(ReduceOps.java:169) [rt.jar:1.8.0_151]
	at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1380) [rt.jar:1.8.0_151]
	at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481) [rt.jar:1.8.0_151]
	at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471) [rt.jar:1.8.0_151]
	at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:708) [rt.jar:1.8.0_151]
	at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234) [rt.jar:1.8.0_151]
	at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:499) [rt.jar:1.8.0_151]
	at org.ovirt.engine.core.bll.storage.utils.BlockStorageDiscardFunctionalityHelper.vmDiskWithPassDiscardAndWadExists(BlockStorageDiscardFunctionalityHelper.java:174) [bll.jar:]
	at org.ovirt.engine.core.bll.storage.utils.BlockStorageDiscardFunctionalityHelper.getLunsThatBreakPassDiscardSupport(BlockStorageDiscardFunctionalityHelper.java:189) [bll.jar:]
	at org.ovirt.engine.core.bll.storage.utils.BlockStorageDiscardFunctionalityHelper.logIfLunsBreakStorageDomainDiscardFunctionality(BlockStorageDiscardFunctionalityHelper.java:130) [bll.jar:]
	at org.ovirt.engine.core.bll.storage.domain.SyncLunsInfoForBlockStorageDomainCommand.updateLunsInDb(SyncLunsInfoForBlockStorageDomainCommand.java:219) [bll.jar:]
	at org.ovirt.engine.core.bll.storage.domain.SyncLunsInfoForBlockStorageDomainCommand.lambda$executeCommand$0(SyncLunsInfoForBlockStorageDomainCommand.java:87) [bll.jar:]
	at org.ovirt.engine.core.utils.transaction.TransactionSupport.executeInNewTransaction(TransactionSupport.java:202) [utils.jar:]
	... 99 more

Expected results:
The following log should appear:
2017-11-29 11:26:27,435+02 INFO  [org.ovirt.engine.core.bll.storage.domain.SyncLunsInfoForBlockStorageDomainCommand] (EE-ManagedThreadFactory-engine-Thread-211) [16178042] Updated LUNs information, IDs '3514f0c5a51600489, 3514f0c5a5160048a'.