Send RPC to non-owner after original owner is killed is not stable in Carbon

As tracked here:

https://jenkins.opendaylight.org/releng/view/openflowplugin/job/openflowplugin-csit-3node-clustering-only-carbon/584/robot/openflowplugin-clustering.txt/Cluster%20HA%20Owner%20Failover/Send%20RPC%20Add%20to%20Successor%20and%20Verify%20After%20Fail/

We get ERROR when trying to push an RPC flow from not-owner instance after original owner is killed:

{"errors":{"error":[

{"error-type":"application","error-tag":"operation-failed","error-message":"The operation encountered an unexpected error while executing.","error-info":"akka.pattern.AskTimeoutException: Ask timed out on [Actor[akka.tcp://opendaylight-cluster-data@10.29.12.203:2550/user/rpc/broker#-1313599470]] after [15000 ms]. Sender[null] sent message of type \"org.opendaylight.controller.remote.rpc.messages.ExecuteRpc\".\n\tat akka.pattern.PromiseActorRef$$anonfun$1.apply$mcV$sp(AskSupport.scala:604)\n\tat akka.actor.Scheduler$$anon$4.run(Scheduler.scala:126)\n\tat scala.concurrent.Future$InternalCallbackExecutor$.unbatchedExecute(Future.scala:601)\n\tat scala.concurrent.BatchingExecutor$class.execute(BatchingExecutor.scala:109)\n\tat scala.concurrent.Future$InternalCallbackExecutor$.execute(Future.scala:599)\n\tat akka.actor.LightArrayRevolverScheduler$TaskHolder.executeTask(LightArrayRevolverScheduler.scala:329)\n\tat akka.actor.LightArrayRevolverScheduler$$anon$4.executeBucket$1(LightArrayRevolverScheduler.scala:280)\n\tat akka.actor.LightArrayRevolverScheduler$$anon$4.nextTick(LightArrayRevolverScheduler.scala:284)\n\tat akka.actor.LightArrayRevolverScheduler$$anon$4.run(LightArrayRevolverScheduler.scala:236)\n\tat java.lang.Thread.run(Thread.java:745)\n"}

]}}