HDFS-5031. BlockScanner scans the block multiple times. (Vinay via Arpit Agarwal)

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HDFS-5122. Support failover and retry in WebHdfsFileSystem for NN HA. Contributed by Haohui Mai.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1524562 13f79535-47bb-0310-9956-ffa450edef68
Move HDFS-5122 from Release 2.1.1-beta to Release 2.3.0 in CHANGES.txt

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