heat engine : fix variable/import shadowing in service.py
heat engine : fix variable/import shadowing in service.py

The resources import is shadowed by a variable declaration in
validate template, which is confusing, so add a prefix to
differentiate the variable from the import

bug 1133434

Change-Id: Ia7c451c3a2588ddff114da9897b3bcf58e68cf0c

noironetworks/heat,redhat-openstack/heat,cwolferh/heat-scratch,maestro-hybrid-cloud/heat,miguelgrinberg/heat,dims/heat,ntt-sic/heat,pratikmallya/heat,openstack/heat,steveb/heat,pshchelo/heat,noironetworks/heat,srznew/heat,dims/heat,pratikmallya/heat,gonzolino/heat,JioCloud/heat,varunarya10/heat,citrix-openstack-build/heat,NeCTAR-RC/heat,rdo-management/heat,rdo-management/heat,rh-s/heat,NeCTAR-RC/heat,cryptickp/heat,varunarya10/heat,JioCloud/heat,Triv90/Heat,miguelgrinberg/heat,cryptickp/heat,srznew/heat,ntt-sic/heat,redhat-openstack/heat,pshchelo/heat,rickerc/heat_audit,jasondunsmore/heat,dragorosson/heat,Triv90/Heat,rh-s/heat,Triv90/Heat,gonzolino/heat,cwolferh/heat-scratch,maestro-hybrid-cloud/heat,citrix-openstack-build/heat,takeshineshiro/heat,jasondunsmore/heat,takeshineshiro/heat,steveb/heat,rickerc/heat_audit,openstack/heat,dragorosson/heat