The existing implementation lacks notification between libvirt packages
and libvirt services, so the services were not restarted even when
libvirt packages are updated.
This fixes it and adds the following notification routes.
- the core libvirtd package notifies all services
- the service package(such as virtqemud) notifies a specific service
Change-Id: Ic9ed4126ddd594a3cbd3a2f9bcb22400167a4a8f
efeb1a944b