HDFS-5288. Merging change r1544352 from trunk

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YARN-1320. Fixed Distributed Shell application to respect custom log4j properties file. Contributed by Xuan Gong.
svn merge --ignore-ancestry -c 1544364 ../../trunk/


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HDFS-5407. Merging change r1544362 from trunk

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Merge HDFS-5544. Adding Test case For Checking dfs.checksum.type as NULL value. Contributed by Sathish.

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HDFS-5444. Merge change r1541753 from trunk.

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HDFS-5525. Merge change r1543895 from trunk.

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HDFS-5552. Merge change r1544627 from trunk.

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