HADOOP-9078. enhance unit-test coverage of class org.apache.hadoop.fs.FileContext (Ivan A. Veselovsky via jeagles)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1532928 13f79535-47bb-0310-9956-ffa450edef68
HDFS-5360. Improvement of usage message of renameSnapshot and deleteSnapshot. Contributed by Shinichi Yamashita.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1532930 13f79535-47bb-0310-9956-ffa450edef68
HDFS-4376. Fix race conditions in Balancer.  Contributed by Junping Du


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1532932 13f79535-47bb-0310-9956-ffa450edef68
Move HDFS-5360 to 2.2.1 in CHANGES.txt

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1532935 13f79535-47bb-0310-9956-ffa450edef68
HDFS-5334. Implement dfshealth.jsp in HTML pages. Contributed by Haohui Mai.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1532949 13f79535-47bb-0310-9956-ffa450edef68