dlm: fix uninitialized variable for search_rsb_list callers

gcc 4.3.0 correctly emits the following warning.
search_rsb_list does not *r_ret if no dlm_rsb is found
and _search_rsb may pass the uninitialized value upstream
on the error path when both calls to search_rsb_list
return non-zero error.

The fix sets *r_ret to NULL on search_rsb_list's not-found path.
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: David Teigland <teigland@redhat.com>

fs/dlm/lock.c

@@ -363,6 +363,7 @@ static int search_rsb_list(struct list_head *head, char *name, int len,
 		if (len == r->res_length && !memcmp(name, r->res_name, len))
 			goto found;
 	}
+	*r_ret = NULL;
 	return -EBADR;
 
  found: