HDFS-6951. Correctly persist raw namespace xattrs to edit log and fsimage. Contributed by Charles Lamb.
Update CHANGES.txt for HDFS-6951
HDFS-6981. Fix DN upgrade with layout version change. (Arpit Agarwal)
HDFS-6981. Fix CHANGES.txt
Merge branch 'trunk' into HDFS-6581

Conflicts:
	hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNodeLayoutVersion.java