Don't send multiple update-cancel messages to an event
Don't send multiple update-cancel messages to an event

Change-Id: Ib64da11ed5584c1a2eef98378d3201a6949fac7d
Closes-Bug: #1376900

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