Fix warning about using os.tempnam in test suite.
Fix warning about using os.tempnam in test suite.

Change-Id: Ibd725071ccdd9af951034685880f35ac678feae2

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