nat: Two fixes for the write memory case...

Add new BSCs to the tail so we keep the sort order when writing
them out to the vty, fix the LAC command.
diff --git a/openbsc/src/nat/bsc_nat_utils.c b/openbsc/src/nat/bsc_nat_utils.c
index 36a64b7..74d8407 100644
--- a/openbsc/src/nat/bsc_nat_utils.c
+++ b/openbsc/src/nat/bsc_nat_utils.c
@@ -74,7 +74,7 @@
 	conf->nr = nat->num_bsc;
 	conf->nat = nat;
 
-	llist_add(&conf->entry, &nat->bsc_configs);
+	llist_add_tail(&conf->entry, &nat->bsc_configs);
 	++nat->num_bsc;
 
 	conf->stats.sccp.conn = counter_alloc("nat.bsc.sccp.conn");