Merge branch '3.1.x'

* 3.1.x:
  [ticket/14394] Only purge cache in functional tests if necessary

tests/test_framework/phpbb_functional_test_case.php

@@ -89,7 +89,6 @@ class phpbb_functional_test_case extends phpbb_test_case
 		// that were added in other tests are gone
 		$this->lang = array();
 		$this->add_lang('common');
-		$this->purge_cache();
 
 		$db = $this->get_db();