Set workers min=0
Set workers min=0

In start_wsgi we assume workers >= 0, but min is None by default.
So we add min=0 here.

Change-Id: Idd5433e9fb0b0bc9c7d897dc397d36ed0b5e0e52

stackforge/senlin,openstack/senlin,openstack/senlin,stackforge/senlin,openstack/senlin