HDFS-4581. Merge r1461615 from branch-1

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1.2@1491535 13f79535-47bb-0310-9956-ffa450edef68
HDFS-4699. Merge r1469843 from branch-1

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1.2@1491539 13f79535-47bb-0310-9956-ffa450edef68
HDFS-4880. Merge r1490758 from branch-1

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1.2@1491541 13f79535-47bb-0310-9956-ffa450edef68
HDFS-4261. Merge r1488865 from branch-1

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1.2@1491544 13f79535-47bb-0310-9956-ffa450edef68