HDFS-6234. Merging change r1586682 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1586686 13f79535-47bb-0310-9956-ffa450edef68
HADOOP-8826. Docs still refer to 0.20.205 as stable line (Mit Desai via jeagles)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1586687 13f79535-47bb-0310-9956-ffa450edef68
HDFS-6235. Merging change r1586692 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1586696 13f79535-47bb-0310-9956-ffa450edef68
HDFS-6229. Merge r1586714 from trunk.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1586715 13f79535-47bb-0310-9956-ffa450edef68