HDFS-6351. Command hdfs dfs -rm -r can't remove empty directory. Contributed by Yongjun Zhang.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1594037 13f79535-47bb-0310-9956-ffa450edef68
HDFS-6230. Merge r1594040 from trunk.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1594041 13f79535-47bb-0310-9956-ffa450edef68
svn merge -c 1594055 merging from trunk to branch-2 to fix:HDFS-5522. Datanode disk error check may be incorrectly skipped. Contributed by Rushabh Shah.

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Merge r1594085 from trunk. YARN-2016. Fix a bug in GetApplicationsRequestPBImpl to add the missed fields to proto. Contributed by Junping Du

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