When responder dies, the requestor doesn't get failed messages.

[Dmitry Kiselev]

When an Accelio Server(Responder) drops just closes, while Accelio client keeps sending, the Accelio client gets a number of on_msg_error callbacks for all the failed messages, but they are all blank without any data and with NULL user_context in each one.

Steps to reproduce:

Server Side:
- Create a Server and make accept 1 connection.
- Poll for one incoming message and close the Server.

Client Side:
- Connect a client to the Server above.
- Then send the same outgoing message 1000 times without waiting for anything.

Verify: the xio_msg* parameter passed in the following callback:
on_msg_error(xio_session*, xio_status, xio_msg *, void *conn_user_context)
doesn't match the message that was send 100 times.