Created attachment 1426084 [details]
engine log

Description of problem:
Create template fail sometimes 

I have failed to create a template from VM one time on latest 4.2.3.2-0.1.el7
Although it reproduced only one time for me, i was suggested by ahadas to report a bug for infar team.

2018-04-24 15:29:53,451+03 ERROR [org.ovirt.engine.core.bll.tasks.CommandCallbacksPoller] (EE-ManagedThreadFactory-engineScheduled-Thread-92) [8cb0d685-cd01-42d2-89f3-3343
1c432fde] Error invoking callback method 'doPolling' for 'ACTIVE' command '23c5f099-8e4b-4ed8-90ea-8c2dd7d3c506'
2018-04-24 15:29:53,458+03 INFO  [org.ovirt.engine.core.bll.tasks.SPMAsyncTask] (EE-ManagedThreadFactory-engine-Thread-415) [8cb0d685-cd01-42d2-89f3-33431c432fde] BaseAsyn
cTask::removeTaskFromDB: Removed task 'a1ace998-b168-4733-aab3-c7d206d03b60' from DataBase
2018-04-24 15:29:53,458+03 INFO  [org.ovirt.engine.core.bll.tasks.CommandAsyncTask] (EE-ManagedThreadFactory-engine-Thread-415) [8cb0d685-cd01-42d2-89f3-33431c432fde] Comm
andAsyncTask::HandleEndActionResult [within thread]: Removing CommandMultiAsyncTasks object for entity '4d66bdb2-bd61-4da0-a9c0-7ee060913860'
2018-04-24 15:29:53,452+03 ERROR [org.ovirt.engine.core.bll.tasks.CommandCallbacksPoller] (EE-ManagedThreadFactory-engineScheduled-Thread-92) [8cb0d685-cd01-42d2-89f3-3343
1c432fde] Exception: java.util.ConcurrentModificationException
        at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:909) [rt.jar:1.8.0_161]
        at java.util.ArrayList$Itr.next(ArrayList.java:859) [rt.jar:1.8.0_161]
        at org.ovirt.engine.core.bll.ChildCommandsCallbackBase.doPolling(ChildCommandsCallbackBase.java:41) [bll.jar:]
        at org.ovirt.engine.core.bll.tasks.CommandCallbacksPoller.invokeCallbackMethodsImpl(CommandCallbacksPoller.java:145) [bll.jar:]
        at org.ovirt.engine.core.bll.tasks.CommandCallbacksPoller.invokeCallbackMethods(CommandCallbacksPoller.java:106) [bll.jar:]
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [rt.jar:1.8.0_161]
        at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308) [rt.jar:1.8.0_161]
        at org.glassfish.enterprise.concurrent.internal.ManagedScheduledThreadPoolExecutor$ManagedScheduledFutureTask.access$201(ManagedScheduledThreadPoolExecutor.java:38
3) [javax.enterprise.concurrent.jar:1.0.0.redhat-1]
        at org.glassfish.enterprise.concurrent.internal.ManagedScheduledThreadPoolExecutor$ManagedScheduledFutureTask.run(ManagedScheduledThreadPoolExecutor.java:534) [jav
ax.enterprise.concurrent.jar:1.0.0.redhat-1]
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [rt.jar:1.8.0_161]
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [rt.jar:1.8.0_161]
        at java.lang.Thread.run(Thread.java:748) [rt.jar:1.8.0_161]
        at org.glassfish.enterprise.concurrent.ManagedThreadFactoryImpl$ManagedThread.run(ManagedThreadFactoryImpl.java:250) [javax.enterprise.concurrent.jar:1.0.0.redhat-
1]
        at org.jboss.as.ee.concurrent.service.ElytronManagedThreadFactory$ElytronManagedThread.run(ElytronManagedThreadFactory.java:78)

2018-04-24 15:29:54,818+03 ERROR [org.ovirt.engine.core.bll.AddVmTemplateCommand] (EE-ManagedThreadFactory-engineScheduled-Thread-62) [8cb0d685-cd01-42d2-89f3-33431c432fde
] Ending command 'org.ovirt.engine.core.bll.AddVmTemplateCommand' with failure.

Version-Release number of selected component (if applicable):
4.2.3.2-0.1.el7

How reproducible:
Reproduced 1 time for me. On second attempt it worked

Steps to Reproduce:
1. Create template from VM

Actual results:
Failed with exception on engine side

Expected results:
Should work