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