Avoid deserializing jobs just for counts

[davetron5000]

Problem

To render the counts per queue on the waiting page, we fetch all jobs in that resque, deserializing them, then count them per queue, basically throwing out all the job data, which we don't need. This is super slow

Solution

Stop doing that and instead just fetch the counts, which is already supported by the backend.

[davetron5000]

This leaves the "get waiting jobs" stuff around. I don't think it's being used, but I only want to do one thing at a time.