bus: use ENXIO as error condition when trying to exit a container when we are not...

bus: use ENXIO as error condition when trying to exit a container when we are not in any

So far we used ENXIO whenever the user tried to read something from a
function that didn't carry the right type, and hence use the same error
here to indicate that what the user expected and what was in the message
didn't match up.