Fixes anonymous user on MySQL.
MySQL import might have set the uid of the anonymous user to autoincrement value. Let's try fixing it. See http://drupal.org/node/204411
public function fixAnonymousUid() {
$this->database
->update('users')
->expression('uid', 'uid - uid')
->condition('name', '')
->condition('pass', '')
->condition('status', 0)
->execute();
}