Add queue-length test.

[Steve Kemp]

For paranoia purposes I have a cronjob which monitors the queue length of pending-jobs.

Add a test to measure a queue length to overseer and it can monitor itself. Unless the worker(s) are dead, of cours!

[Steve Kemp]

This is what we want:

  localhost must run redis with set 'overseer.jobs' with max_size 1000

Horrid syntax, but required due to our current approach.

set could be list too, for a similar test.