Fixed valve device class by removed _finished_moving

This branch fix the wrong behavior of the valve device class, when it was used together with other controlling components, like phoebus or the controlling rack (described in WP #3596, https://openproject.helmholtz-berlin.de/projects/bluesky/work_packages/3596/activity). When the valve was close not by the valve device class, there was no _update_setpoint(), so _finished_moving was not set to 0. After the status changes of the valve the _update_readback was triggered, but _finished_moving was not 0, so the readbacks were not set properly.

Also changed the condition to only toggle if the setpoint is 1 or 0, before it was toggling every time it not matched the readback, so it always toggle for a setpoint>=2 regardless to the readback value.