HDFS-5943. Merge 1568412 from trunk

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HDFS-5768. Merge change r1558598 from trunk.

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HDFS-5775. Merge change r1558599 from trunk.

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YARN-1553. Modified YARN and MR to stop using HttpConfig.isSecure() and
instead rely on the http policy framework. And also fix some bugs related
to https handling in YARN web-apps. Contributed by Haohui Mai.
svn merge --ignore-ancestry -c 1568501 ../../trunk/


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HDFS-3128. Unit tests should not use a test root in /tmp. (wang)

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