Stop the network interface after kernel is loaded but before starting it.

Not doing this caused packets to be read into memory somewhere after the
kernel was started but before the device was probed, normally in the
system page table. This gave quite unpredictable results...

sys/arch/vax/boot/boot/netio.c

@@ -1,4 +1,4 @@
-/*	$NetBSD: netio.c,v 1.3 1999/05/07 16:19:28 drochner Exp $	*/
+/*	$NetBSD: netio.c,v 1.4 1999/06/30 18:38:03 ragge Exp $	*/
 
 /*-
  * Copyright (c) 1996, 1997 The NetBSD Foundation, Inc.
@@ -140,6 +140,7 @@ int
 netclose(f)
 	struct open_file *f;
 {
+	netif_close(netdev_sock);
 	f->f_devdata = NULL;
 }