Add a convenience method to get instance volumes
Add a convenience method to get instance volumes

Change-Id: If22cd9245b043f35386ad3c24d46a41b0b8c2c86

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