zebra: fix more compiler warnings

* zebra/zebra_rib.c
  * nexthop_active_update(): make local int vars unsigned
  * nexthop_active_check(): return unsigned for consistency
  * rib_dump(): cast time in printf format
  * vrf_free(): remove unused function
  * vrf_lookup_by_name(): idem
  * rib_if_up(): idem
  * rib_if_down(): idem
1 file changed