Merge -c 1499566 from branch-1 to branch-1.2 to fix MAPREDUCE-5364. Deadlock between RenewalTimerTask methods cancel() and run(). (kkambatl via tucu)

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MAPREDUCE-5364. Committed to branch-1.2 also.

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Merge -c 1499902 from branch-1 to branch-1.2 to fix MAPREDUCE-5375. Use short name for renewing delegation tokens. Contributed by Venkat Ranganathan.

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Merge -c 1499904 from branch-1 to branch-1.2 to fix MAPREDUCE-5351. Addedndum patch to ensure we don't incorrectly close wrong filesystems. Contributed by Sandy Ryza.

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Merge -c 1499906 from branch-1 to branch-1.2 to fix MAPREDUCE-5368. Reduce memory footprint of JobTracker by using non-default values for hash-tables to store Locality and Avataar for TaskAttempts. Contributed by zhaoyunjiong.

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