XD-1739: Container reconnection to ZK fails intermittently

If a container disconnects and reconnects to ZooKeeper, sometimes the ephemeral node for that container isn't cleaned up before the container attempts to create a new ephemeral node. This fix will delete the node if it exists prior to creating a new one.

In theory this should never happen, but in cases where the ZK server and the container are both suspended (i.e. a laptop goes to sleep) the container could reconnect before ZK cleans up the old ephemeral node.

Also added the `@SuppressWarnings("serial")` annotation to `ZooKeeperAccessException`.