Remove lockfile from requirements
Remove lockfile from requirements

It is not used anymore by Heat.

Change-Id: I1095084e7ecdaac5655f7f4cd78473be49d17d8a

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