Fixed warnings, behat error and deprecated warnings.

auth.php

@@ -57,6 +57,8 @@ class auth_plugin_outage extends auth_plugin_base {
 
     /**
      * Always returns false (password wrong or user does not exist).
+     *
+     * @inheritdoc PHPMD will not warn about unused parameters if overriding.
      * @param string $username Not used in this plugin.
      * @param string $password Not used in this plugin.
      * @return bool False