HADOOP-9509. Merging change r1499156 from branch-2

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2.1.0-beta@1499503 13f79535-47bb-0310-9956-ffa450edef68
HADOOP-9515. Merging change r1499167 from branch-2

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2.1.0-beta@1499504 13f79535-47bb-0310-9956-ffa450edef68
HDFS-4762,HDFS-4948,HDFS-4954. Merging change r1499190,r1499321 from branch-2

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2.1.0-beta@1499509 13f79535-47bb-0310-9956-ffa450edef68