Copy 'oldlabel' to 'newlabel' when we read it - should mean that

sysinst 'upgrade' will find the correct filesystem type and install
the correct boot code.
Fixes PR install/24812

distrib/utils/sysinst/disks.c

@@ -1,4 +1,4 @@
-/*	$NetBSD: disks.c,v 1.74 2003/11/30 14:36:43 dsl Exp $ */
+/*	$NetBSD: disks.c,v 1.75 2004/03/26 17:28:55 dsl Exp $ */
 
 /*
  * Copyright 1997 Piermont Information Systems Inc.
@@ -197,6 +197,9 @@ find_disks(const char *doingwhat)
 	/* Get existing/default label */
 	incorelabel(diskdev, oldlabel);
 
+	/* Set 'target' label to current label in case we don't change it */
+	memcpy(&bsdlabel, &oldlabel, sizeof bsdlabel);
+
 	return numdisks;
 }