[Sprint/PinkPanther](fix): Upload cancelling #2083

Closes #2083 (closed) Credits to Mark for the elegant solution

Summary

Upload cancellation is broken on production. Go upload a video on it and try to cancel it.

Test

1. Upload a video, & whilst uploading, upload a second video - it should replace the existing upload, progress bar should not jump erratically.
2. Try cancelling the upload. it should cancel. - Without a refresh, try to upload a second video.
3. Uploading a video should complete all the way and post.
4. Should not interfere with image upload.