HDFS-6948. DN rejects blocks if it has older UC block. Contributed by
Eric Payne.
HDFS-7065. Pipeline close recovery race can cause block corruption.
Contributed by Kihwal Lee.
HDFS-7096.  Fix TestRpcProgramNfs3 to use DFS_ENCRYPTION_KEY_PROVIDER_URI (clamb via cmccabe)
Merge branch 'trunk' into HDFS-6581