MDL-70107 tool_task: Unlock session on long running tasks in UI

admin/tool/task/schedule_task.php

@@ -83,6 +83,8 @@ function tool_task_mtrace_wrapper($message, $eol) {
 // Action requires session key.
 require_sesskey();
 
+\core\session\manager::write_close();
+
 // Prepare to handle output via mtrace.
 echo html_writer::start_tag('pre');
 $CFG->mtrace_wrapper = 'tool_task_mtrace_wrapper';