We did a small VNFM here in Stockholm some time ago which was a ConfD on top of libvirt (no openstack) It was called gabbleduck. An experiment.
I know we had a vm-manager-gabbleduck at the time. Anyways this is at least a usecase.
The ESC team has ESC-lite, which is something similar. Maybe it is entirely compatible with ESC (I think it is ??) thus no additional vm-manager-xx is needed.
/klacke