Avoid skipping ranges when looping through queues

[francesmcmullin]

When queues are very full and/or very active, the ruby reaper can't give absolute guarantees because it doesn't run as a single atomic action, but we can eliminate some edge cases.

In this instance, the reaper anticipates that a queue might empty, from the front, in which case ranges need to be adjusted downward to ensure every job is checked. However, in the case where the queue grows (at the back), this calculation of "next_page - (initial_size - current_size))" means skipping over some jobs.

[mhenrixon]

Rebasing with master will give you a green build on the first two PRs.

[mhenrixon]

Whatever is left is all on you 😋

[francesmcmullin]

Green now 🎉 🟢 Thanks for the nudge ^_^