https://bugzilla.redhat.com/show_bug.cgi?id=924501 tracks a
problem that occurs if uid 107 is already in use at the time
libvirt is first installed.  In response that problem, Fedora
packaging guidelines were recently updated.  This fixes the
spec file to comply with the new guidelines:
https://fedoraproject.org/wiki/Packaging:UsersAndGroups

* libvirt.spec.in (daemon): Follow updated Fedora guidelines.
Signed-off-by: NEric Blake <eblake@redhat.com>