HADOOP-10894: Merging r1613200 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1613201 13f79535-47bb-0310-9956-ffa450edef68
HDFS-6723. Merge r1613220 from trunk.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1613222 13f79535-47bb-0310-9956-ffa450edef68
HDFS-6715. Merge r1613237 from trunk.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1613239 13f79535-47bb-0310-9956-ffa450edef68