Set random manager ProcessWID if empty

[heitorgo1]

Set the manager ProcessWID to the same random value as the Faktory client's ProcessWID when one is not provided.

[mperham]

I'm trying to understand why we didn't set this before. In Faktory's model, a process can either be a job producer (using the basic Faktory client to push jobs) or a consumer (a worker process fetching jobs to execute). I'm unclear when faktory.RandomProcessWID and mgr.ProcessWID should be different or if there are usecases which this change might break. Faktory is really stable at this point and I don't want to introduce a subtle bug for someone.