HDFS-4372. Merging change r1502419 from branch-2 to branch-2.1-beta.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2.1-beta@1502420 13f79535-47bb-0310-9956-ffa450edef68
HDFS-4373. Merging change r1502423 from branch-2 to branch-2.1-beta.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2.1-beta@1502424 13f79535-47bb-0310-9956-ffa450edef68
HDFS-4374. Merging change r1502426 from branch-2 to branch-2.1-beta.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2.1-beta@1502427 13f79535-47bb-0310-9956-ffa450edef68