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.


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1611734 13f79535-47bb-0310-9956-ffa450edef68
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