heat tests : Add utility decorator for deleting stacks
heat tests : Add utility decorator for deleting stacks

Add decorator function which allows test functions to be wrapped
such that if they create a stack (and it is stored in the testcase
class as self.stack) it is always deleted on test exit, regardless
of test success/failure

Change-Id: Ibde9a2cee08448e3f24c6b7efbfe756a01f9eccc
Signed-off-by: Steven Hardy <4d1810d1ff6d7f22d774341c4549c02173d2f2ab@redhat.com>

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