bgpd, zebra: Use next hop tracking for connected routes too

Allow next hop tracking to work with connected routes
And cleanup obsolete code in bgp_scan and bgp_import.

Signed-off-by: Dinesh Dutt <ddutt@cumulusnetworks.com>
Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>
Edits: Paul Jakma <paul.jakma@hpe.com> Rebase re-ordering conflicts with
       NHT route-map, potential errors.
diff --git a/bgpd/bgp_fsm.h b/bgpd/bgp_fsm.h
index 752d6e2..b38e64c 100644
--- a/bgpd/bgp_fsm.h
+++ b/bgpd/bgp_fsm.h
@@ -72,6 +72,7 @@
   } while (0)
 
 /* Prototypes. */
+extern void bgp_fsm_nht_update(struct peer *, int valid);
 extern int bgp_event (struct thread *);
 extern int bgp_stop (struct peer *peer);
 extern void bgp_timer_set (struct peer *);