executor: broadcast while locked

It's legal to do it after the lock but we always do it while locked, as
most (if not all) implementations handle this specific case.

src/misc/executor.c

@@ -266,11 +266,11 @@ vlc_executor_Delete(vlc_executor_t *executor)
     /* All the tasks must be canceled on delete */
     assert(vlc_list_is_empty(&executor->queue));
 
-    vlc_mutex_unlock(&executor->lock);
-
     /* "closing" is now true, this will wake up threads */
     vlc_cond_broadcast(&executor->queue_wait);
 
+    vlc_mutex_unlock(&executor->lock);
+
     /* The threads list may not be written at this point, so it is safe to read
      * it without mutex locked (the mutex must be released to join the
      * threads). */