CI: reduce api worker processes to 1
CI: reduce api worker processes to 1

CI is memory intensive, and we realistically don't need 2 or
more API workers running for every single WSGI process which
does not implement it's own specific override value.

This should reduce the memory footprint by an average of six processes
which consume 60-90 MB each.

Change-Id: Ia0a986152c2b9fc9c5ff54cf698a351db452fbbd

openstack/ironic,openstack/ironic