rtsp-media: update expected_async_done during suspend

Set expected_async_done to FALSE in default_suspend() if a state change
occurs and the return value from set_target_state() is something other
than GST_STATE_CHANGE_ASYNC.

Without this change there is a risk that expected_async_done will be
TRUE even though no asynchronous state change is taking place. This
could happen if the pipeline is set to PAUSED using
media_set_pipeline_state_locked(), an asynchronous state change starts
and then the media is suspended (which could result in a state change,
aborting the asynchronous state change). If the media is suspended
before the asynchronous state change ends then expected_async_done will
be TRUE but no asynchronous state change is taking place.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-rtsp-server/-/merge_requests/123>

gst/rtsp-server/rtsp-media.c

@@ -4444,7 +4444,7 @@ static gboolean
 default_suspend (GstRTSPMedia * media)
 {
   GstRTSPMediaPrivate *priv = media->priv;
-  GstStateChangeReturn ret;
+  GstStateChangeReturn ret = GST_STATE_CHANGE_FAILURE;
 
   switch (priv->suspend_mode) {
     case GST_RTSP_SUSPEND_MODE_NONE:
@@ -4472,6 +4472,12 @@ default_suspend (GstRTSPMedia * media)
       break;
   }
 
+  /* If we use any suspend mode that changes the state then we must update
+   * expected_async_done, since we might not be doing an asyncronous state
+   * change anymore. */
+  if (ret != GST_STATE_CHANGE_FAILURE && ret != GST_STATE_CHANGE_ASYNC)
+    priv->expected_async_done = FALSE;
+
   return TRUE;
 
   /* ERRORS */