EOF is not always an error case

EOF is not always an error case

From the docs:

> If the read direction of the socket has shutdown, then the filter
> also sets EV_EOF in flags, and returns the socket error (if any) in
> fflags. It is possible for EOF to be returned (indicating the
> connection is gone) while there is still data pending in the socket
> buffer.

So we suppress printing an error on normal EOF.  Instead, we just
see if we need to reconnect the socket.

Arguably if the other end closes our read side, we _might_ be able
to write to the socket?  but we could still write to it.