Handle tcp-ip-forward global request responses.

[jimmyvanhest]

When a tcp-ip-forward global request is sent a REQUEST_SUCCESS or a REQUEST_FAILURE response is expected and should be handled. this is also an opportunity to parse and return the port number returned by the server.

[Eugeny]

Welcome and thank you for your contribution!

Unfortunately read_u32 is failing when there's no port info in the request (e.g. in the success response of the cancel-tcpip-forward request)

The session should either remember the type of the last global request and act accordingly or in the worst case, just ignore a missing port field.