RIKENFE: Clicking "Off" sets setpoint to zero

On RIKENFE with the Danfysik OPI used for RB3 and RB4: clicking "Off" also sets the setpoint to zero such that subsequently clicking "On" does not restore normal operation. This shouldn't happen, the setpoint should be unchanged.

## Acceptance criteria:

- [ ] Investigate whether this needs to be an option or should be the only behaviour
- [ ] If it needs to be an option: the user can set an option in the danfysik to set the setpoint to zero when pressing off
- [ ] If it needs to be the default: when pressing "Off" the setpoint is not set to zero