Merged revision(s) 1604692 from hadoop/common/trunk:
HDFS-6507. Improve DFSAdmin to support HA cluster better. (Contributd by Zesheng Wu)
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git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1604695 13f79535-47bb-0310-9956-ffa450edef68