for ID19 shutters : to not change id19 configs, shutter times are still read
                    from config in milliseconds and converted to seconds
ccd_shutter_time : if not specified in config, set to None. When controlling
                   shutter with CCD, if a fast shutter exist (soft_shutter in
                   config), use its closing time. If not fast shutter configured
                   then use default ccd_shutter_time (in seconds)