XD-2004: Containers stopped responding to Admin

Fixed race condition between the container creating the `/xd/deployments/modules/allocated/container-id` path and the supervisor removing the path when the container exits. The container will now wait for the supervisor to remove the path before proceeding with startup.

Added onSuspend and onResume to ZooKeeperConnectionListener. This allows us to distinguish between events where container ephemeral nodes need to be created after a network disconnect.

Temporary network disconnects will raise `SUSPENDED` events followed by `RECONNECTED` events. Containers will now avoid undeploying modules upon `SUSPENDED` events. `LOST` events still cause modules to be undeployed. `RECONNECTED` events will force a shutdown and recreation of the ZooKeeper client if the prior event was `LOST`. If the prior event was `SUSPENDED`, the container will re-register if the existing ephemeral node for that container was created by the previous ZooKeeper client session.

Testing was done on Linux via iptables DROP rules. Additionally, testing was performed with a ZooKeeper ensemble, including the shut down of 2 out of 3 servers to disrupt quorum.
Great catch! I had added these delete methods before because I was experimenting with explicitly deleting the ephemeral nodes on startup. It turns out that this is a bad idea because the existence of an ephemeral node when the container joins the cluster means one of two things:
* The container's ZK session is still alive, and the ZK server considers the container to be in a good state
* The container's prior ZK session has not expired yet

The 2nd case is especially problematic - if I delete and recreate the container's ephemeral node, the ephemeral nodes for its prior deployments are still present, and everyone thinks the container has deployed those modules when it has not.

This is why the container will now wait for the prior session to expire before continuing - thus eliminating the need to delete the container's ephemeral node explicitly. I will revert these changes to the repository and push.