Scheduled action no interrupt

At the end of the run, ScheduledAction unsubscribes itself which triggers a set of cleanup actions, and since it is also the way to cancel a running action, it calls future.cancel(true) as well which interrupts the task in the underlying executor framework. However, on a normal completion path, it is unnecessary to interrupt itself at the end of the run since it will complete anyway, and not to mention, it has some performance implications for short running tasks. The downside is the +4 bytes per ScheduledAction.
> or cancel.unsubscribe() is called which is idempotent.

This is the part that I wasn't sure of, so if that is idempotent then there definitely is not a need for the extra ONCE_UPDATER. Thanks for walking me through this patiently.