Fix for adding datanode master in pgxc_ctl. Locking DDL was not

correct.   The locking function pgxc_lock_for_backup() was issued
against a datanode but it should be targetted to a coordinator.

Author: koichi-szk

contrib/pgxc_ctl/datanode_cmd.c

@@ -1003,7 +1003,7 @@ add_datanodeMaster(char *name, char *host, int port, char *dir)
 	}
 
 	/* Lock ddl */
-	if ((lockf = pgxc_popen_wRaw("psql -h %s -p %d %s", aval(VAR_datanodeMasterServers)[0], atoi(aval(VAR_datanodePorts)[0]), sval(VAR_defaultDatabase))) == NULL)
+	if ((lockf = pgxc_popen_wRaw("psql -h %s -p %d %s", aval(VAR_coordMasterServers)[0], atoi(aval(VAR_coordPorts)[0]), sval(VAR_defaultDatabase))) == NULL)
 	{
 		elog(ERROR, "ERROR: could not open psql command, %s\n", strerror(errno));
 		return 1;