Fix unit tests in totara 10

- Change outagelib_test to use the auth_outage_base_testcase base class
  - Remove outages from test table in tearDown function after each test.

tests/phpunit/base_testcase.php

@@ -74,4 +74,9 @@ abstract class auth_outage_base_testcase extends advanced_testcase {
         $CFG->wwwroot = 'http://www.example.com/moodle';
         $CFG->httpswwwroot = $CFG->wwwroot;
     }
+
+    public function tearDown() {
+        global $DB;
+        $DB->delete_records('auth_outage');
+    }
 }

tests/phpunit/local/outagelib_test.php

@@ -41,7 +41,7 @@ require_once($CFG->libdir.'/adminlib.php');
  * @license     http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  * @SuppressWarnings(public) Allow as many methods as needed.
  */
-class outagelib_test extends advanced_testcase {
+class outagelib_test extends auth_outage_base_testcase {
     /**
      * Check if maintenance message is disabled as needed.
      */