HDFS-7124. Remove EncryptionZoneManager.NULL_EZ. (clamb via wang)
YARN-2606. Application History Server tries to access hdfs before doing secure login (Mit Desai via jeagles)
HDFS-7122. Use of ThreadLocal<Random> results in poor block placement. (wang)
HADOOP-11153. Make number of KMS threads configurable. (wang)
HADOOP-11130. NFS updateMaps OS check is reversed. Contributed by Brandon Li
Merge branch 'trunk' into HDFS-6581