HDFS-6597. Merging change r1611723 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1611724 13f79535-47bb-0310-9956-ffa450edef68
fix eol style on TestBootstrapStandbyWithBKJM

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1611727 13f79535-47bb-0310-9956-ffa450edef68
svn merge -c 1611731 from trunk for HDFS-6700. BlockPlacementPolicy shoud choose storage but not datanode for deletion.


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svn merge -c 1611737 FIXES: HDFS-6599. 2.4 addBlock is 10 to 20 times slower compared to 0.23 (daryn)


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1611738 13f79535-47bb-0310-9956-ffa450edef68
svn merge -c 1611750 from trunk for HDFS-6616. Add exclude-datanodes feature to WebHDFS redirection so that it will not redirect retries to the same datanode.


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HADOOP-10817. ProxyUsers configuration should support configurable prefixes. (tucu)

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HDFS-6632. Reintroduce dfs.http.port / dfs.https.port in branch-2. Contributed by Yongjun Zhang.

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Move CHANGES.txt info for HDFS-6632 from 2.6 to 2.5 section.


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