svn merge -c 1565310 merging from trunk to branch-2 to fix: HDFS-5881. Fix skip() of the short-circuit local reader(legacy).

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1565313 13f79535-47bb-0310-9956-ffa450edef68
MAPREDUCE-5699. Allow setting tags on MR jobs (kasha)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1565385 13f79535-47bb-0310-9956-ffa450edef68
HADOOP-10327. Merging change r1565389 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1565390 13f79535-47bb-0310-9956-ffa450edef68
YARN-1661. Fixed DS ApplicationMaster to write the correct exit log. Contributed by Vinod Kumar Vavilapalli.
svn merge --ignore-ancestry -c 1565394 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1565397 13f79535-47bb-0310-9956-ffa450edef68
MAPREDUCE-5743. Fixed CHANGES.txt to give credit to Ted too.
svn merge --ignore-ancestry -c 1565401 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1565402 13f79535-47bb-0310-9956-ffa450edef68
HDFS-4911. Reduce PeerCache timeout to be commensurate with dfs.datanode.socket.reuse.keepalive (cmccabe)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1565438 13f79535-47bb-0310-9956-ffa450edef68
HDFS-5895. Merging change r1565440 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1565442 13f79535-47bb-0310-9956-ffa450edef68