Student profile CSV background task tech debt

TNL-525

These 4 commits address 4 fairly small instances of technical debt that @nasthagiri and I came across while working on the backgroundify student profile CSV story.

@jimabramson @nasthagiri please review.

@cahrens FYI
You can reduce the number of lines in this method considerably if you:
1. set default values for the `_update_task_progress method`.
2. don't create one-time used intermediate variables unnecessarily.