Don't touch web.config when flushing rewrite rules if it is a multisite install. Fixes #16076 props nacin.

git-svn-id: https://develop.svn.wordpress.org/trunk@17328 602fd350-edb4-49c9-b593-d223f7449a82

wp-admin/includes/misc.php

@@ -149,6 +149,9 @@ function save_mod_rewrite_rules() {
  * @return bool True if web.config was updated successfully
  */
 function iis7_save_url_rewrite_rules(){
+	if ( is_multisite() )
+		return;
+
 	global $wp_rewrite;
 
 	$home_path = get_home_path();