fixed password decoding

We decoded the wrong option here before.

lib/plugins/authad/auth.php

@@ -642,7 +642,7 @@ class auth_plugin_authad extends DokuWiki_Auth_Plugin {
         // compatibility with old option name
         if(empty($opts['admin_username']) && !empty($opts['ad_username'])) $opts['admin_username'] = $opts['ad_username'];
         if(empty($opts['admin_password']) && !empty($opts['ad_password'])) $opts['admin_password'] = $opts['ad_password'];
-        $opts['ad_password'] = conf_decodeString($opts['ad_password']); // deobfuscate
+        $opts['admin_password'] = conf_decodeString($opts['admin_password']); // deobfuscate
 
         // we can change the password if SSL is set
         if($opts['use_ssl'] || $opts['use_tls']) {