Merge 1550074 from trunk: HDFS-5580. Fix infinite loop in Balancer.waitForMoveCompletion. (Binglin Chang via junping_du)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1550078 13f79535-47bb-0310-9956-ffa450edef68