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/trunk@1594036 13f79535-47bb-0310-9956-ffa450edef68
HDFS-6230. Expose upgrade status through NameNode web UI. Contributed by Mit Desai.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1594040 13f79535-47bb-0310-9956-ffa450edef68
HDFS-5522. Datanode disk error check may be incorrectly skipped. Contributed by Rushabh Shah.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1594055 13f79535-47bb-0310-9956-ffa450edef68
YARN-2016. Fix a bug in GetApplicationsRequestPBImpl to add the missed fields to proto. Contributed by Junping Du

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1594085 13f79535-47bb-0310-9956-ffa450edef68
HDFS-6326: correct web UI display
HDFS-6326: code review feedback
Merge branch 'trunk' into HDFS-6326