HDFS-5252. Stable write is not handled correctly in someplace. Contributed by Brandon Li

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1539740 13f79535-47bb-0310-9956-ffa450edef68
HDFS-5443. Delete 0-sized block when deleting an under-construction file that is included in snapshot. Contributed by Jing Zhao.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1539754 13f79535-47bb-0310-9956-ffa450edef68
HDFS-5468. CacheAdmin help command does not recognize commands  (Stephen Chu via Colin Patrick McCabe)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1539786 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/trunk' into trunk-gd
Merge remote branch 'origin/trunk-gd' into fb-HDFS-4312-trunk-gd