Fix tests after making qa-base.php access the database

qa-tests/autoload.php

 <?php
 // currently, all Q2A code depends on qa-base
+
+global $qa_options_cache;
+
+// Needed in order to avoid accessing the database while including the qa-base.php file
+$qa_options_cache['enabled_plugins'] = '';
+
 require_once __DIR__.'/../qa-include/qa-base.php';