iichid(4): Unify two taskqueue tasks

taskqueue_enqueue_timeout(0) is equivalent to taskqueue_enqueue(),
so no need to create a separate periodic_task and event_task to run
exactly the same handler.

MFC after: 1 month

(cherry picked from commit a8f80c0c16c7fb38c46ddccd7e1b06dc46c407b1)