#651086 follow-up by carols8f: Fix cache clearing is an ineffective mess.

includes/common.inc

includes/install.core.inc

includes/module.inc

includes/update.inc

modules/simpletest/drupal_web_test_case.php

modules/simpletest/tests/module_test.module

modules/simpletest/tests/upgrade/upgrade.test

modules/system/system.admin.inc

modules/system/system.install

modules/system/system.module

modules/system/system.test