Ifdef out a redundant if statement when INET6 is disabled.

MFC after:	1 week

contrib/ipfilter/tools/ippool.c

@@ -1047,7 +1047,9 @@ setnodeaddr(int type, int role, void *ptr, char *arg)
 	if (type == IPLT_POOL) {
 		ip_pool_node_t *node = ptr;
 
+#ifdef USE_INET6
 		if (node->ipn_addr.adf_family == AF_INET)
+#endif
 			node->ipn_addr.adf_len = offsetof(addrfamily_t,
 							  adf_addr) +
 						 sizeof(struct in_addr);