function scheduler_addIdleTask(id, priority, queue, count) {
  scheduler_addRunningTask.call(this, id, priority, queue, new IdleTask(this, 1, count));
}
Add an idle task to this scheduler.
@param {int} id the identity of the task
@param {int} priority the task's priority
@param {Packet} queue the queue of work to be processed by the task
@param {int} count the number of times to schedule the task