Description of problem:
After upgrading to 4.1.7.6 environment with running vms (and vm pools),
Engine failed to start. 


Version-Release number of selected component (if applicable):
4.1.7.6

How reproducible:
All the   time

Steps to Reproduce:
Upgrade engine from 4.1.7.5 to 4.1.7.6

Actual results:
Web admin not reachable 


Server log:
2017-10-31 22:19:33,028+02 INFO  [org.quartz.impl.StdSchedulerFactory] (ServerService Thread Pool -- 59) Quartz scheduler 'DefaultQuartzScheduler' initialized from default resource file in Quartz package: 'quartz.properties'
2017-10-31 22:19:33,028+02 INFO  [org.quartz.impl.StdSchedulerFactory] (ServerService Thread Pool -- 59) Quartz scheduler version: 2.1.2
2017-10-31 22:19:33,028+02 INFO  [org.quartz.core.QuartzScheduler] (ServerService Thread Pool -- 59) Scheduler DefaultQuartzScheduler_$_NON_CLUSTERED started.
2017-10-31 22:19:33,168+02 INFO  [org.jboss.as.clustering.infinispan] (ServerService Thread Pool -- 59) WFLYCLINF0002: Started timeout-base cache from ovirt-engine container
2017-10-31 22:19:39,282+02 ERROR [org.jboss.as.ejb3.invocation] (ServerService Thread Pool -- 59) WFLYEJB0034: EJB Invocation failed on component MacPoolPerCluster for method public void org.ovirt.engine.core.bll.network.macpool.MacPoolPerCluster.logFreeMacs(): javax.ejb.EJBException: java.lang.IllegalStateException: WFLYEE0042: Failed to construct component instance
        at org.jboss.as.ejb3.tx.CMTTxInterceptor.handleExceptionInOurTx(CMTTxInterceptor.java:187) [wildfly-ejb3-7.0.8.GA-redhat-1.jar:7.0.8.GA-redhat-1]
        at org.jboss.as.ejb3.tx.CMTTxInterceptor.invokeInOurTx(CMTTxInterceptor.java:277) [wildfly-ejb3-7.0.8.GA-redhat-1.jar:7.0.8.GA-redhat-1]
        at org.jboss.as.ejb3.tx.CMTTxInterceptor.required(CMTTxInterceptor.java:327) [wildfly-ejb3-7.0.8.GA-redhat-1.jar:7.0.8.GA-redhat-1]
        at org.jboss.as.ejb3.tx.CMTTxInterceptor.processInvocation(CMTTxInterceptor.java:239) [wildfly-ejb3-7.0.8.GA-redhat-1.jar:7.0.8.GA-redhat-1]
        at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:340)
        at org.jboss.invocation.InterceptorContext$Invocation.proceed(InterceptorContext.java:437)
        at org.jboss.weld.ejb.AbstractEJBRequestScopeActivationInterceptor.aroundInvoke(AbstractEJBRequestScopeActivationInterceptor.java:64) [weld-core-impl.jar:2.3.3.Final-redhat-1]
        at org.jboss.as.weld.ejb.EjbRequestScopeActivationInterceptor.processInvocation(EjbRequestScopeActivationInterceptor.java:83) [wildfly-weld-7.0.8.GA-redhat-1.jar:7.0.8.GA-redhat-1]
        at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:340)
        at org.jboss.as.ejb3.component.interceptors.CurrentInvocationContextInterceptor.processInvocation(CurrentInvocationContextInterceptor.java:41) [wildfly-ejb3-7.0.8.GA-redhat-1.jar:7.0.8.GA-redhat-1]
        at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:340)
        at org.jboss.as.ejb3.component.invocationmetrics.WaitTimeInterceptor.processInvocation(WaitTimeInterceptor.java:43) [wildfly-ejb3-7.0.8.GA-redhat-1.jar:7.0.8.GA-redhat-1]
        at org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:340)
        at org.jboss.as.ejb3.security.SecurityContextInterceptor.processInvocation(SecurityContextInterceptor.java:100) [wildfly-ejb3-7.0.8.GA-redhat-1.jar:7.0.8.GA-redhat-1]
......
.....
 AND :
2017-10-31 22:19:45,831+02 INFO  [org.wildfly.extension.undertow] (ServerService Thread Pool -- 58) WFLYUT0021: Registered web context: /ovirt-engine/sso
2017-10-31 22:19:45,890+02 ERROR [org.jboss.as.controller.management-operation] (Controller Boot Thread) WFLYCTL0013: Operation ("deploy") failed - address: ([("deployment" => "engine.ear")]) - failure description: {"WFLYCTL0080: Failed services" => {"jboss.deployment.subunit.\"engine.ear\".\"bll.jar\".component.Backend.START" => "org.jboss.msc.service.StartException in service jboss.deployment.subunit.\"engine.ear\".\"bll.jar\".component.Backend.START: java.lang.IllegalStateException: WFLYEE0042: Failed to construct component instance
    Caused by: java.lang.IllegalStateException: WFLYEE0042: Failed to construct component instance
    Caused by: javax.ejb.EJBException: java.lang.IllegalStateException: WFLYEE0042: Failed to construct component instance
    Caused by: java.lang.IllegalStateException: WFLYEE0042: Failed to construct component instance
    Caused by: javax.ejb.EJBException: java.lang.RuntimeException: org.ovirt.engine.core.utils.ovf.OvfReaderException: OVF error: win_12_pool-1: cannot read 'VmInit' with value: null
    Caused by: java.lang.RuntimeException: org.ovirt.engine.core.utils.ovf.OvfReaderException: OVF error: win_12_pool-1: cannot read 'VmInit' with value: null
    Caused by: org.ovirt.engine.core.utils.ovf.OvfReaderException: OVF error: win_12_pool-1: cannot read 'VmInit' with value: null"}}