This was causing some confusing conflicts, so create a new fact called
"this_node" which is inventory_hostname.split('.')[0], i.e. the short
name, and use that everywhere instead of an FQDN or true inventory
hostname.
This has no functional change on Buster, but on Bullseye this overrides
the stupid socket-based activation shenanigans that the default unit
tries to do, as well as the breaking replacement of the
/etc/default/libvirt variable names.