Optionally close incoming connection when `Session` is not enabled

[chrjohn]

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Follow up to #360 where an incoming connection is rejected via a Logout message when the session is not enabled.

It should also be possible to just close the incoming connection in AcceptorIoHandler when the session's enabled flag is false. Probably it would be best if this was configurable.

https://github.com/quickfix-j/quickfixj/blob/77f21e77fd7229e0a08c983d376ba5a2ee1bede3/quickfixj-core/src/main/java/quickfix/mina/acceptor/AcceptorIoHandler.java#L62-L69 ...