Use yaml.safe_load: full yaml.load isn't needed
Use yaml.safe_load: full yaml.load isn't needed

The only reason to use yaml.load instead of safe_load is if one wants to
load serialized objects. Heat's use case is purely to load basic data
structures such as maps/lists/strings. Fixes bug #1117820

Change-Id: I4f6cf2ed4e15405f8b296ccaec737a3779c9867d

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