HDFS-5859.  DataNode#checkBlockToken should check block tokens even if security is not enabled (cmccabe)

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HDFS-5804. Merge change r1563323 from trunk.

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YARN-1633. Defined user-facing entity, entity-info and event objects related to Application Timeline feature. Contributed by Zhijie Shen.
svn merge -c 1563356 ../../trunk/


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HDFS-5746.  Add ShortCircuitSharedMemorySegment (cmccabe)

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