Add -sit back to demo friction test.

Perhaps we should put it with friction test in actual sessions rather
than with force offset?
Remove unnecessary protocols from demo menu.
Try to avoid residual messages.

An out-dated ‘status’ screen will sometimes show briefly before a
‘query’ screen appears. Here I tried to fix it for the specific case of
the Audio test and for the final ‘Task Completed’ screen in general. It
could perhaps be made better in other tasks as well.