bgpd, plug rtlabel refcount leak on network statements

[Claudio Jeker]

Found while working on kroute code. The network structs needs to release
the rtlabel reference before being freed.

-- 
:wq Claudio

Index: config.c
===================================================================
RCS file: /cvs/src/usr.sbin/bgpd/config.c,v
retrieving revision 1.102
diff -u -p -r1.102 config.c
--- config.c    5 Jun 2022 12:43:13 -0000       1.102
+++ config.c    19 Jul 2022 16:52:40 -0000
@@ -92,6 +92,7 @@ free_networks(struct network_head *netwo
 
        while ((n = TAILQ_FIRST(networks)) != NULL) {
                TAILQ_REMOVE(networks, n, entry);
+               rtlabel_unref(n->net.rtlabel);
                filterset_free(&n->net.attrset);
                free(n);
        }