Shut down client actor on auth failure

[mmacfadden]

When authentication fails, we send an auth failure back to the client. However, we essentially then wait for the client to disconnect. We would like to shut down the client actor as soon as we know the auth failure has been sent out. This is challenging because we don't actually know when that message is sent.

It seems like we need a way to know when a message has been sent to the connection actor from the protocol actor. Potentially using a future or something. This way we could take an action after we know the message has been sent.