Use the variable set up for when the function doesn't exist.

git-svn-id: http://svn.automattic.com/wordpress/trunk@15022 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/network.php

@@ -358,8 +358,8 @@ define( 'BLOG_ID_CURRENT_SITE', 1 );</textarea>
 ?>
 </li>
 <?php
-	if (iis7_supports_permalinks()) {
-			if (is_subdomain_install()) {
+	if ( iis7_supports_permalinks() ) {
+			if ( $subdomain_install ) {
 				$web_config_file =
 '<?xml version="1.0" encoding="UTF-8"?>
 <configuration>