Follow-up from "Use a background migration for migrating issues.closed_at"
The following discussion from !16083 (merged) should be addressed:
Do we need to add any limit on how many times this can be rescheduled?
Once https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/16083 is merged we need a separate MR for 10.5 that ensures the migrations are done by stealing any remaining jobs in a regular migration. In 99% of the cases this won't end up processing any jobs, but it's better to be safe than sorry.