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
HDFS-5364. Add OpenFileCtx cache. Contributed by Brandon Li

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1539834 13f79535-47bb-0310-9956-ffa450edef68
HDFS-5326. add modifyDirective to cacheAdmin (cmccabe)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1539839 13f79535-47bb-0310-9956-ffa450edef68
Merging r1539737 through r1539896 from trunk to branch HDFS-2832

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