Since moving to libvirt nova-compute poller we no longer have
the availability_zone attribute of an instance available.
We can capture instance.create.end events and create gnocchi resources
based on these which do have the availability_zone availabile.
Currently we are only handling delete events for resources, this
patch adds the handling of create events for this purpose.
Change-Id: Ieddbddd4ddb6af11d5158f5c90c87ae4f847bb96
21a810fec6