Assume sideband and aes_ctr128 are always supported/requested.

Assume sideband and aes_ctr128 are always supported/requested.

Sideband connections and the AES-based stream cipher have become
mandatory in paraslash-0.6.

The server no longer needs to annouce the feature as 0.6.x clients
request it, regardless of whether it was announced or not. It needs
to still accept the option, though.

On the client side, we don't need to request the features any more
as the server just ignores the request.