Figure out if we need to "flush" messages before exiting the server/client

[perarnau]

I have seen tests where it looks like a client is receiving notifications that the server exited before receiving an ACK message on the command. This might be a symptom of the server exiting before all the messages in flights have been sent.

[perarnau]

Reopening as an existing problem on exit command.
My guess is that we need to make the two roles switch to a receive-only/send-only mode for the last message supposed to be sent out.