HDFS-4876. Merging change r1490117 from branch-2.

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HDFS-4850. Merging change r1490084 from branch-2

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HDFS-4877. Merging r1490430 from branch-2.

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YARN-777. Removed unreferenced objects from .proto files. Contributed by Jian He.
svn merge --ignore-ancestry -c 1490882 ../../trunk/


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YARN-642. Removed health parameter from ResourceManager /nodes web-service and cleaned the behaviour of the status parameter. Contributed by Sandy Ryza.
svn merge --ignore-ancestry -c 1490890 ../../trunk/


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