rtspsrc: fix major memory leak when playing back rtsp video streams

Don't forget to unref QoS, navigation and latency events when
dropping them.

gst/rtsp/gstrtspsrc.c

@@ -1699,6 +1699,7 @@ gst_rtspsrc_handle_internal_src_event (GstPad * pad, GstEvent * event)
     case GST_EVENT_NAVIGATION:
     case GST_EVENT_LATENCY:
     default:
+      gst_event_unref (event);
       res = TRUE;
       break;
   }