MDL-67211 Tasks: Add cron_enabled setting.

Co-authored-by: Sam Marshall <[email protected]>

admin/tool/task/scheduledtasks.php

@@ -95,6 +95,9 @@ if ($mform && ($mform->is_cancelled() || !empty($CFG->preventscheduledtaskchange
 
 } else {
     echo $OUTPUT->header();
+    if (!get_config('core', 'cron_enabled')) {
+        echo $renderer->cron_disabled();
+    }
     $tasks = core\task\manager::get_all_scheduled_tasks();
     echo $renderer->scheduled_tasks_table($tasks, $lastchanged);
     echo $OUTPUT->footer();