HDFS-5634. Allow BlockReaderLocal to switch between checksumming and not (cmccabe)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1552119 13f79535-47bb-0310-9956-ffa450edef68
HDFS-5662. Merging change r1552131 from trunk

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1552135 13f79535-47bb-0310-9956-ffa450edef68
HDFS-5676. fix inconsistent synchronization of CachingStrategy (cmccabe)

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HDFS-5661. Merge change r1552177 from trunk.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1552180 13f79535-47bb-0310-9956-ffa450edef68
YARN-1307. Redesign znode structure for Zookeeper based RM state-store for better organization and scalability. Contributed by Tsuyoshi OZAWA.
svn merge --ignore-ancestry -c 1552209 ../../trunk/


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