Set statuscode=404 in NotFoundException in tests
Set statuscode=404 in NotFoundException in tests

when resource can'n be found,neutron will set
statuscode=404 in NotFoundException,so add statuscode
in exception to make fake client have same action.

Change-Id: I6597f080903501d9fe6050893054cc7dba6a595b

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