[flakey test] TestZooKeeper

I observed a test failure in TestZooKeeper#testMasterSessionExpired on my local rig. On a casual read of the logs from testMasterSessionExpired, it appears we have a faulty assumption related to master MTTR; the master abort is logged ~1250ms after ZK session close, which seems entirely too fast to me. Once the master aborts, the damage is done and the test cannot recover.

The first re-run passes. Surefire does not keep logs of successful tests, so I don't know the timing between events in the successful run.