Split the rollback transaction by date

We are seeing mysql locks with large rollbacks, splitting by date
should reduce the chances of this happening.

We should be covered by the redis-lock preventing other processes
using the db while this happens
Remove the retry options from the worker, in preperation for manual
retries
Merge pull request #182 from alphagov/step-rollback

Split the rollback transaction by date
Merge pull request #183 from alphagov/rollback-retry

Remove the retry options from the worker