Burn ins are not composited onto media renders using the MRQ

In 5.1 media exports will not have the burn in composited onto them. 

1. Ensure the  Avid DNx Media plugin is enabled
2. Add a sequence to a render job in the MRQ
3. Add an Avid DNX export setting
4. Add a burn in setting, make sure Composite Onto final Image is checked
5. Render locally

RESULT

The avid DNX output does not have the burn in composited onto it. Compare to 5.0, where it does.