pf: Fix rule evaluation after inet6 route-to

In pf_route6() we re-run the ruleset with PF_FWD if the packet goes out
of a different interface. pf_test6() needs to know that the packet was
forwarded (in case it needs to refragment so it knows whether to call
ip6_output() or ip6_forward()).

This lead pf_test6() to try to evaluate rules against the PF_FWD
direction, which isn't supported, so it needs to treat PF_FWD as PF_OUT.
Once fwdir is set correctly the correct output/forward function will be
called.

PR:		217883
Submitted by:	Kajetan Staszkiewicz
MFC after:	1 week
Sponsored by:	InnoGames GmbH

sys/netpfil/pf/pf.c

@@ -6245,6 +6245,9 @@ pf_test6(int dir, struct ifnet *ifp, struct mbuf **m0, struct inpcb *inp)
 	    m->m_pkthdr.rcvif->if_bridge != ifp->if_bridge)))
 		fwdir = PF_FWD;
 
+	if (dir == PF_FWD)
+		dir = PF_OUT;
+
 	if (!V_pf_status.running)
 		return (PF_PASS);