Remove spurious tracebacks from tests, part 2
Remove spurious tracebacks from tests, part 2

Added the same fix that was applied to the other stack_delete tests in
ed7710cd3 to test_stack_delete_other_dead_engine_active_lock.

Change-Id: I3a81844bd6c21013e5956fce9ff9fe5508fcbd94
Closes-Bug: #1278836

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