Always resolve properties against the current stack
Always resolve properties against the current stack

During an update, resources can get moved around between stacks. Ensure
that the properties are always resolved against whatever the current stack
is, without needing to replace self.properties.

Change-Id: I09f984cdf4478ca7dda2b0a0f1aa5a63dd2c19bc

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