[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.
I didn't see it because once ActiveAE i done playing back it closes the stream which restores the previous streamformat (which is likely unencoded) before the next initialize then reactivates the callback. Though i don't like it really somehow :( - ideas?