bgpd: use F_RIB_HASNOFIB

[Denis Fondras]

cosmetic/consistency change

F_RIB_HASNOFIB is defined so let's use it.

Index: kroute.c
===================================================================
RCS file: /cvs/src/usr.sbin/bgpd/kroute.c,v
retrieving revision 1.224
diff -u -p -r1.224 kroute.c
--- kroute.c    29 Sep 2018 19:25:32 -0000      1.224
+++ kroute.c    4 Nov 2018 19:58:19 -0000
@@ -381,7 +381,7 @@ ktable_update(u_int rtableid, char *name
                }
        }
 
-       if (flags & (F_RIB_NOEVALUATE | F_RIB_NOFIB))
+       if (flags & F_RIB_HASNOFIB)
                /* only rdomain table must exist */
                return (0);