The logic around what gets shown on the uploads page was hard to follow.
This commit makes three changes to hopefully make it easier:
- remove the passing-around of a string containing the contents of a
rendered partial
- encapsulate everything in one `show_scheduled_jobs` variable, rather
than mixing between `scheduled_jobs` and
`current_service.scheduled_jobs`
- adds a comment to explain why we still render `_jobs.html` even when
we know we have no jobs