HDFS-4693. Merge r1468457 from trunk.

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HADOOP-8562. Merge r1469996 for HADOOP-9488, r1469998 for YARN-593

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MAPREDUCE-4987. Merge r1470003  from trunk

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HADOOP-9443. Merge r1470224 from trunk

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HDFS-4725. Merge r1470771 from trunk

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HDFS-4732. Merge r1471090 from trunk

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HDFS-3131. Merge r1305688 from trunk

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HDFS-4741. Merge r1476585 from trunk

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HADOOP-9290. Merge r1476586 from trunk

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HDFS-4743. Merge r1476591 from trunk

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HDFS-4740. Merge r1476596 from trunk

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HDFS-4722. Merge r1476597 from trunk

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HADOOP-9500. Merge r1476606 from trunk

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HADOOP-9490. Merge r1476609 from trunk

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HDFS-4705. Merge r1476610 from trunk

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