AM hangs when running tests

[hungj]

For example, it hangs here: testTensorBoardPortSetOnlyOnChiefWorker

2019-10-02 23:44:28 INFO  ApplicationMaster:886 - Received result registration request with exit code 0 from chief 0
2019-10-02 23:44:28 INFO  ApplicationMaster:893 - Unregistering task [chief:0] from Heartbeat monitor..
2019-10-02 23:44:31 INFO  ApplicationMaster:851 - All 3 tasks registered.
2019-10-02 23:44:31 INFO  ApplicationMaster:851 - All 3 tasks registered.
2019-10-02 23:44:31 INFO  ApplicationMaster:886 - Received result registration request with exit code 0 from worker 0
2019-10-02 23:44:31 INFO  ApplicationMaster:893 - Unregistering task [worker:0] from Heartbeat monitor..
2019-10-02 23:44:31 INFO  ApplicationMaster:886 - Received result registration request with exit code 0 from ps 0
2019-10-02 23:44:31 INFO  ApplicationMaster:893 - Unregistering task [ps:0] from Heartbeat monitor..
2019-10-02 23:44:59 INFO  Client:871 - Retrying connect to server: . Already tried 0 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
2019-10-02 23:45:00 INFO  Client:871 - Retrying connect to server: . Already tried 1 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
2019-10-02 23:45:01 INFO  Client:871 - Retrying connect to server: . Already tried 2 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
2019-10-02 23:45:02 INFO  Client:871 - Retrying connect to server: . Already tried 3 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
2019-10-02 23:45:03 INFO  Client:871 - Retrying connect to server: . Already tried 4 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)

All three tasks unregistered with AM, but then ipc.Client retry policy kicks in which causes test to exceed 10 min timeout. Seems it's trying to talk to RM, probably to unregisterApplicationMaster, but can't contact it for some reason.