High finesse does not represent state of wavemeter accurately

[drogenlied]

Migration: trac#68.

highfinesse.stop_acquisition() gave a warning about it already being stopped, despite that not being true. Doing highfinesse.start_acquisition() and then repeating the stop command gave no such error.

This seemed to have implications for the remote connection, since problems there disappeared once we had the highfinesse module accurately aware of its state.