Merge HDFS-5789. Some of snapshot APIs missing checkOperation double check in fsn. Contributed by Uma Maheswara Rao G.

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svn merge -c 1560761 FIXES: HDFS-5241. Provide alternate queuing audit logger to reduce logging contention (daryn)


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svn merge -c 1560750 merging from trunk to branch-2 to fix:HDFS-5788. listLocatedStatus response can be very large. Contributed by Nathan Roberts.

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