If a systemd socket uses /var/run in its path, systemd prints a warning
at runtime

[   15.139976] systemd[1]: /usr/lib/systemd/system/virtlockd.socket:5:
  ListenStream= references a path below legacy directory /var/run/,
  updating /var/run/libvirt/virtlockd-sock → /run/libvirt/virtlockd-sock;
  please update the unit file accordingly.

This minimal change updates the socket unit files to honour the
$runstatedir path.

There's no functional change by default yet since both expressions
expand to the same value.
Reviewed-by: NMichal Privoznik <mprivozn@redhat.com>
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>