[ticket/14315] Add logout to ui tests and use in permissions role test

PHPBB3-14315

tests/ui/permission_roles_test.php

@@ -19,6 +19,7 @@ class ui_permission_roles_test extends phpbb_ui_test_case
 
 	public function test_permission_roles()
 	{
+		$this->logout();
 		$this->login();
 		$this->admin_login();
 		$this->add_lang('acp/permissions');