HDFS-7387. Merging to branch-2.6 for hadoop-2.6.0-rc1.

(cherry picked from commit 09f36b1)

Conflicts:
	hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

Author: acmurthy

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -618,6 +618,9 @@ Release 2.6.0 - 2014-11-15
     HDFS-7383. DataNode.requestShortCircuitFdsForRead may throw 
     NullPointerException. (szetszwo via suresh)
 
+    HDFS-7387. NFS may only do partial commit due to a race between COMMIT and write
+    (brandonli)
+
     BREAKDOWN OF HDFS-6581 SUBTASKS AND RELATED JIRAS
 
       HDFS-6921. Add LazyPersist flag to FileStatus. (Arpit Agarwal)