vaapisink: update res with automatic rotation tag
requested to merge den_erpel/gstreamer:gstreamer-vaapi/vaapisink-correct-resolution-from-tag into main
ensure_resolution returned too early when an update was received with an event instead of a property. This resulted in a correct resolution; but the image was stretched with the wrong rotation.
Only allow the function to return prematurely when the update was not from a tag/event.