HDFS-5596. Implement RPC stubs. Contributed by Haohui Mai.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/HDFS-4685@1550544 13f79535-47bb-0310-9956-ffa450edef68
HDFS-5595: initial testing of AclTransformation.
Merge branch 'HDFS-4685' into HDFS-5595