Fix output accounting when a bridge is down

[Martin Pieuchot]

When a bridge is not in RUNNING state packets are simply enqueued on the
interface.  But since the introduction of bridge_ifenqueue() they are
accounted as being sent through the bridge.  Diff below fixes that by
calling if_enqueue() directly.

ok?

Index: net/if_bridge.c
===================================================================
RCS file: /cvs/src/sys/net/if_bridge.c,v
retrieving revision 1.325
diff -u -p -r1.325 if_bridge.c
--- net/if_bridge.c     12 Mar 2019 11:45:00 -0000      1.325
+++ net/if_bridge.c     29 Mar 2019 13:27:59 -0000
@@ -737,8 +737,10 @@ bridge_output(struct ifnet *ifp, struct 
         */
        sc = bif->bridge_sc;
        if ((sc->sc_if.if_flags & IFF_RUNNING) == 0) {
-               dst_if = ifp;
-               goto sendunicast;
+               /* Loop prevention. */
+               m->m_flags |= M_PROTO1;
+               error = if_enqueue(ifp, m);
+               return (error);
        }
 
 #if NBPFILTER > 0
@@ -810,7 +812,6 @@ bridge_output(struct ifnet *ifp, struct 
                return (0);
        }
 
-sendunicast:
        if ((dst_if->if_flags & IFF_RUNNING) == 0) {
                m_freem(m);
                return (ENETDOWN);