HDFS-4772. Merging change r1495253 from trunk

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1495535 13f79535-47bb-0310-9956-ffa450edef68
Merge r1495533 from trunk to branch-2 for YARN-827. Need to make Resource arithmetic methods accessible (Jian He via bikas)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1495538 13f79535-47bb-0310-9956-ffa450edef68
Update CHANGES.txt to move HDFS-4772 to 2.1.0 section

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1495542 13f79535-47bb-0310-9956-ffa450edef68
Merged HADOOP-9619 svn merge -c 1495564


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1495573 13f79535-47bb-0310-9956-ffa450edef68
svn merge -c 1495577 FIXES: HADOOP-9421. [RPC v9] Convert SASL to use ProtoBuf and provide negotiation capabilities (daryn)


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Merge remote branch 'origin/branch-2' into branch-2-gd