zebra: Fix non usage of VRF_DEFAULT

A vrf_id was being set to 0 instead of VRF_DEFAULT

Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>
diff --git a/zebra/zebra_rib.c b/zebra/zebra_rib.c
index 0efa88d..38357ff 100644
--- a/zebra/zebra_rib.c
+++ b/zebra/zebra_rib.c
@@ -3247,7 +3247,7 @@
     {
 
     case RIB_TABLES_ITER_S_INIT:
-      iter->vrf_id = 0;
+      iter->vrf_id = VRF_DEFAULT;
       iter->afi_safi_ix = -1;
 
       /* Fall through */