Seting worker pool size to 0 results in 3 workers running

[edwardotis]

Current config requires at least one worker to run. However, in a split environment between web and worker apps, the web app should have no worker pool. It should only be enqueuing jobs for the worker app to consume.

This config throws an exception if you set the pool size to < 0. If you it to 0, it uses the default value of 3 instead of 0.