fix mocking of db_api.stack_count_all()
fix mocking of db_api.stack_count_all()

Change-Id: I3de1141898f6444cbb8615943ae0311413babb70

jasondunsmore/heat,noironetworks/heat,rdo-management/heat,jasondunsmore/heat,dragorosson/heat,openstack/heat,pratikmallya/heat,takeshineshiro/heat,miguelgrinberg/heat,cwolferh/heat-scratch,pshchelo/heat,takeshineshiro/heat,miguelgrinberg/heat,cryptickp/heat,cryptickp/heat,pratikmallya/heat,openstack/heat,noironetworks/heat,maestro-hybrid-cloud/heat,srznew/heat,cwolferh/heat-scratch,gonzolino/heat,rh-s/heat,steveb/heat,rdo-management/heat,dims/heat,maestro-hybrid-cloud/heat,dims/heat,dragorosson/heat,gonzolino/heat,steveb/heat,rh-s/heat,srznew/heat,pshchelo/heat