Null pointer exception reported in engine logs after a failed VM import from a RHV export domain

Issue

• As a result of a failed VM import, ovirt-engine reported a null pointer exception;

2017-12-01 16:38:33,349-03 ERROR [org.ovirt.engine.core.bll.tasks.CommandAsyncTask] (org.ovirt.thread.pool-7-thread-41) [] [within thread]: endAction for action type ImportVm threw an except
ion.: java.lang.NullPointerException
        at org.ovirt.engine.core.bll.network.VmInterfaceManager.removeAll(VmInterfaceManager.java:135) [bll.jar:]
        at org.ovirt.engine.core.bll.exportimport.ImportVmCommand.removeVmNetworkInterfaces(ImportVmCommand.java:1178) [bll.jar:]
        at org.ovirt.engine.core.bll.exportimport.ImportVmCommand.endWithFailure(ImportVmCommand.java:1146) [bll.jar:]
        at org.ovirt.engine.core.bll.CommandBase.internalEndWithFailure(CommandBase.java:768) [bll.jar:]
        at org.ovirt.engine.core.bll.CommandBase.endActionInTransactionScope(CommandBase.java:697) [bll.jar:]
        at org.ovirt.engine.core.bll.CommandBase.runInTransaction(CommandBase.java:2057) [bll.jar:]
        at org.ovirt.engine.core.utils.transaction.TransactionSupport.executeInNewTransaction(TransactionSupport.java:202) [utils.jar:]
        at org.ovirt.engine.core.utils.transaction.TransactionSupport.executeInRequired(TransactionSupport.java:137) [utils.jar:]
        at org.ovirt.engine.core.utils.transaction.TransactionSupport.executeInScope(TransactionSupport.java:105) [utils.jar:]
        at org.ovirt.engine.core.bll.CommandBase.endAction(CommandBase.java:559) [bll.jar:]
        at org.ovirt.engine.core.bll.tasks.DecoratedCommand.endAction(DecoratedCommand.java:17) [bll.jar:]
        at org.ovirt.engine.core.bll.tasks.CoCoAsyncTaskHelper.endAction(CoCoAsyncTaskHelper.java:337) [bll.jar:]
        at org.ovirt.engine.core.bll.tasks.CommandCoordinatorImpl.endAction(CommandCoordinatorImpl.java:340) [bll.jar:]
        at org.ovirt.engine.core.bll.tasks.CommandAsyncTask.endCommandAction(CommandAsyncTask.java:154) [bll.jar:]
        at org.ovirt.engine.core.bll.tasks.CommandAsyncTask.lambda$endActionIfNecessary$0(CommandAsyncTask.java:106) [bll.jar:]
        at org.ovirt.engine.core.utils.threadpool.ThreadPoolUtil$InternalWrapperRunnable.run(ThreadPoolUtil.java:84) [utils.jar:]
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [rt.jar:1.8.0_144]
        at java.util.concurrent.FutureTask.run(FutureTask.java:266) [rt.jar:1.8.0_144]
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [rt.jar:1.8.0_144]
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [rt.jar:1.8.0_144]
        at java.lang.Thread.run(Thread.java:748) [rt.jar:1.8.0_144]