Refactor Resource's decision whether to update
Refactor Resource's decision whether to update

Split the decision of whether an update is required into a separate method.

Change-Id: I838985a17ab4a5dca48a17d620729117c277c65b

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