ctdb-mutex: Exit immediately if the lock isn't taken

There is no need to wait until the parent kills the helper.  The
parent will get the initial response, indicating contention or
similar, and will then get a separate event indicating that the pipe
is gone.

Signed-off-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Amitay Isaacs <amitay@gmail.com>

ctdb/server/ctdb_mutex_fcntl_helper.c

@@ -101,6 +101,10 @@ int main(int argc, char *argv[])
 	result = fcntl_lock(file, &fd);
 	sys_write(STDOUT_FILENO, &result, 1);
 
+	if (result != '0') {
+		return 0;
+	}
+
 	ctdb_wait_for_process_to_exit(ppid);
 
 	if (fd != -1) {