Lifecycle of objects in retry_upload_pipeline

If you look in ```retry_upload_pipeline``` code is:

```
upload_data = get_upload_data_for_uploaded_file(uploaded_file)
if upload_pipeline.file_type == UploadedFileTypes.VCF:
...
else:
upload_data.delete()
```

Look into whether it's a good idea to just delete the uploaded files? And whether the objects are cleaning up after themselves?

I think I have special case code for a few things, but maybe should do this better