Major Description
The condition to stop the eventHandling thread currently requires it to be 'stopped' AND interrupted. If an interrupt arrives after a take, but before handleEvent is called - the interrupt status ends up being handled by hadoop.util.Shell.runCommand() - which ignores it (and in the process resets the flag).
The eventHandling thread subsequently hangs on eventQueue.take()
This currently randomly fails unit tests - and can hang MR AMs.