https://bugzilla.redhat.com/850186

I added %with_systemd_macros so it should now work in F17 with old
scriptlets and in F18+/RHEL7+ with systemd macros
(see https://fedoraproject.org/wiki/Packaging:ScriptletSnippets#Systemd)

I missed libvirt-guests.service because there is no systemctl call for
it. So I only added systemd macros calls.