Wakeup worker when there are resources freed up

[mavahedinia]

Related to the bug reported on Issue#881.

[mavahedinia]

I would appreciate if you can help me understand why some tests are failing. @agronholm

[agronholm]

Would it be possible for you to add a regression test for this?
As for the other tests failing, I can probably take a look later.

[agronholm]

Oh, and also add a changelog entry (credit yourself too).

[mavahedinia]

I will look into writing tests over the weekend. Thanks for your fast response!

[agronholm]

Any progress on those tests?

[mavahedinia]

Sorry man, I am so busy with moving that haven't had any chance to look at it.

[agronholm]

One issue I have with this PR is that it needlessly wakes up the job processor whenever a job is released, not just when the processor was previously at capacity. Could you fix that?

[agronholm]

But if you're still busy with IRL stuff, let me know and I'll look into fixing it and writing tests.

[coveralls]

coverage: 92.614%. first build
when pulling ce74e1e on mavahedinia:fix-worker-deadlock
into fad16ec on agronholm:master.

[agronholm]

I've added the test and changelog entry on your behalf. Thank you for the contribution!