V2 changes:
 - Keep using /var/lib for the lease file, but making it respect localstatedir
 - Don't pass an empty --conf-file as that confuses dnsmasq when
   /etc/dnsmasq.conf doesn't exist or isn't readable.
Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>