ConcurrentModificationException when updating and deleting a domain from a domain group

[thomas-kielbus]

java.util.ConcurrentModificationException at java.util.HashMap$HashIterator.nextEntry(HashMap.java:793) at java.util.HashMap$EntryIterator.next(HashMap.java:834) at java.util.HashMap$EntryIterator.next(HashMap.java:832) at java.util.AbstractMap.remove(AbstractMap.java:221) at com.rapleaf.hank.coordinator.zk.ZkHostDomain.removePartition(ZkHostDomain.java:107) at com.rapleaf.hank.partition_server.UpdateManager.deletePartition(UpdateManager.java:351) at com.rapleaf.hank.partition_server.UpdateManager.access$100(UpdateManager.java:31) at com.rapleaf.hank.partition_server.UpdateManager$PartitionUpdateTask.run(UpdateManager.java:174) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) at java.lang.Thread.run(Thread.java:662)