HDFS-5219. Merge change r1524498 from trunk.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1524499 13f79535-47bb-0310-9956-ffa450edef68
HDFS-5031. Merge change r1524553 from trunk to branch-2

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1524556 13f79535-47bb-0310-9956-ffa450edef68
HDFS-5122. Merge change r1524562 from trunk.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1524566 13f79535-47bb-0310-9956-ffa450edef68