HADOOP-9875.  TestDoAsEffectiveUser can fail on JDK 7.  (Aaron T. Myers via Colin Patrick McCabe)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1514153 13f79535-47bb-0310-9956-ffa450edef68
svn merge -c 1514156 from trunk for HDFS-4898. BlockPlacementPolicyWithNodeGroup.chooseRemoteRack() fails to properly fallback to local rack.


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1514157 13f79535-47bb-0310-9956-ffa450edef68
HDFS-4632. Merging change r1514168 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1514169 13f79535-47bb-0310-9956-ffa450edef68
merge YARN-1045. Improve toString implementation for PBImpls. Contributed by Jian He.


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1514186 13f79535-47bb-0310-9956-ffa450edef68