HDFS-5638. Merging change r1576405 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1576410 13f79535-47bb-0310-9956-ffa450edef68
Merge r1576513 from trunk.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1576515 13f79535-47bb-0310-9956-ffa450edef68
YARN-1821. NPE on registerNodeManager if the request has containers for UnmanagedAMs (kasha)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1576527 13f79535-47bb-0310-9956-ffa450edef68
HDFS-6086. Fix a case where zero-copy or no-checksum reads were not allowed even when the block was cached. (cmccabe)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1576534 13f79535-47bb-0310-9956-ffa450edef68
YARN-1800. Fixed NodeManager to gracefully handle RejectedExecutionException in the public-localizer thread-pool. Contributed by Varun Vasudev.
svn merge --ignore-ancestry -c 1576545 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1576546 13f79535-47bb-0310-9956-ffa450edef68