[AE/osxsink] - fix possible device changed loop when using passthrough

Damnit - that one slipped in when i added the registration to the default output device changed callback.

@jmarshalnz for review - Gotham material sadly.
We need to enumerate on default output device change. That is why i added this notification in the first place ;). We could though disable the callback whenever the format is altered by us (basically just disable it during the whole initialize call and during the restore call when closing the stream). Not sure if this helps?