Fix schedule hooks firing when timestamp <= now

[top-sigrid]

When enqueue_at is called with a timestamp in the past or equal to now, the job bypasses the delayed queue and goes directly to the work queue. Previously, before_schedule and after_schedule hooks were incorrectly called in this case.

This fix moves process_schedule_hooks inside the else branch so hooks only fire when jobs actually enter the delayed queue.

Fixes #816

[PatrickTulskie]

@top-sigrid I think this is fine to merge, but it could use a rebase. Mind rebasing on master, pushing it up and let's see if CI passes.

[top-sigrid]

Hi Patrick, thanks for getting back to this! I can definitely do that, will find the time very soon. Probably a good idea to do this for my other PRs aswell :)

[PatrickTulskie]

@top-sigrid oh yeah actually you're right there are a few that we can probably merge in once they are rebased. I'm aiming to get a few resque releases out around mid-month. If we can get them in before that they'll make the release. Holler when you want me to check them!

[top-sigrid]

Hi @PatrickTulskie I finally found the time to dedicate some time to this again. This one is rebased and the CI passes so should be fine. Let me know if you have any further wishes or review :)