Reflectometry: On init a motor in the parked position will get an offset of that parked position

@John-Holt-Tessella fill in

1. While doing this consider an non autosaved offset. Currently it gets set to the the offfset, should it be set to 0 if parked. If so create ticket if you can't do it as part of this.

### Notes

In practrise axes that can be parked will have the offset autosaved so this will not be a problem