merged some bug fixes from 1.5:
ACCUMULO-1125 delete distributed work queue task lock when task fails
ACCUMULO-1049 modified master to stop locking tserver nodes and just monitor  tserver nodes in zookeeper
ACCUMULO-954 made zoolock report when its no longer able to monitor lock node and there does not know the status of the lock
ACCUMULO-954 Made zoolock rewatch its parent node and added some unit test for zoolock

git-svn-id: https://svn.apache.org/repos/asf/accumulo/branches/1.4@1451708 13f79535-47bb-0310-9956-ffa450edef68