Fixes #40 Don't Fatal on failure to reset watches.

- Add a test for slow servers
Fix race conditions in tests
Fix continuous loop of connect attempts

Sometimes zookeeper just drops connection on invalid session data,
we prefer to drop session and start from scratch when that event
occurs instead of dropping into loop of connect/disconnect attempts.

This can be emulated by stopping zookeeper, cleaning it's database and
starting it again. But we experience same bug in production without
cleaning zookeeper, but in case of network partition (not every partition
event).
More debugging info on authentication failed thing