also insist that keycount == dscpcount

(cherry picked from commit dbdd1985)

bin/named/config.c

@@ -864,6 +864,7 @@ ns_config_getipandkeylist(const cfg_obj_t *config, const cfg_obj_t *list,
 		isc_mem_put(mctx, stack, stackcount * sizeof(*stack));
 
 	INSIST(keycount == addrcount);
+	INSIST(keycount == dscpcount);
 
 	ipkl->addrs = addrs;
 	ipkl->dscps = dscps;