Fix course image uploads on local storage (CANVAS-263)
Fix course image uploads on local storage (CANVAS-263)

This is a temporary fix. It reverts to the previous behaviour if
successUrl is not available.

Test plan:

* Go to Settings in any course and upload an image
* Verify that the upload works

sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms