svn merge -c 1488865 from branch-1 for HDFS-4261. Fix bugs in Balaner causing infinite loop and TestBalancerWithNodeGroup timeing out.


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1-win@1488867 13f79535-47bb-0310-9956-ffa450edef68