Revert fix as it has caused a deadlock when hanging up (SFR 460576).

Revert "SFR 458544 Prevent an exception being thrown while stream is closed."

This reverts commit 9c1d706c257646252c3aeacb83addcab1bb72613.
Alternate fix for SFR 458544 / 460576.  Having an incoming read() after
close() is a legitimate window, and isn't exceptional; just return without
doing anythign rather than throwing an exception.  That way we won't
end up killing the audio in other narrower windows (458544), nor do we
need any locks that may end up killing all calls (460576).