private void callRpcService(User clientUser) throws Exception {
    callRpcService(User.create(ugi), clientUser);
  }
Sets up a RPC Server and a Client. Does a RPC checks the result. If an exception is thrown from
the stub, this function will throw root cause of that exception.
hbase-server/src/test/java/org/apache/hadoop/hbase/security/AbstractTestSecureIPC.java