svn merge -c 1461597 Merging from trunk to branch-2 to fix HDFS-4581.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1461602 13f79535-47bb-0310-9956-ffa450edef68
YARN-474. Revert since compilations fails: svn merge --change -1461403 .

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1461626 13f79535-47bb-0310-9956-ffa450edef68
YARN-496. Fair scheduler configs are refreshed inconsistently in reinitialize. Contributed by Sandy Ryza

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