Increase number of clients for stress test and remove excessive logging (causes heartbeats to get delayed and the zookeeper session to get severed).
* Removed pipe() state change signaling. We'll just check the state of each topology watcher after we run zookeeper_process(). This will result in more state checks but these are cheap and removing the pipe() signaling simplifies the code.
* Added a getTopologyWatcherZNode() method.