Github user lvfangmin commented on the issue:
https://github.com/apache/zookeeper/pull/689
@anmolnar that's a good point, I think the reason we didn't use
ZooKeeperThread or ZooKeeperCriticalThread is because we don't expect to exit
abnormally from the WatcherCleaner thread, which is true for now. But I think
it's better to use ZooKeeperThread or even ZooKeeperCriticalThread to cover
future changes which might cause the thread exit abnormally.---
