HADOOP-10031. Merging change r1530823 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1530827 13f79535-47bb-0310-9956-ffa450edef68
HDFS-5323.  Remove some deadcode in BlockManager (Colin Patrick McCabe)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1530831 13f79535-47bb-0310-9956-ffa450edef68
HDFS-5337. Merging change r1530835 from trunk

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1530836 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/branch-2' into branch-2-gd
Merge remote branch 'origin/branch-2-gd' into fb-MAPREDUCE-4884-branch-2-gd