-) Introduce a wait-loop with a 100ms delay on iomgr shutdown, so that background threads have the chance to place last minute callbacks without having to stall for the whole 10 seconds deadline.
-) io completion ports will get notifications on socket shutdowns, so we need to delay their deletions for after we get a notification for them.
-) we need to keep some sense of how many orphan sockets are in, so we can properly collect them - let's not shutdown the iocp loop until after all orphans have been collected.