The ipfw script requires the ppp script that's provided by another
package, so the firewall ends up failing closed at the moment as the
script doesn't run without both present. The requirement is fairly
dubious, so let's just pull the transitive dependency on netif into
ipfw and make sure that ppp runs BEFORE ipfw.
Fixes: f91d251b399af ("rc.d: move some rc scripts to their packages")