Reflectometry: 3539-1 Consider using the retry deadband not the motor resolution to see if it has moved

As an instrument scientist, I would like my motors to move only when they are asked to move a greater distance than a given number. This should be done consistently throughout the instrument, so reflectometry IOC and scan library should both use the same field. Retry deadband should probably be that field but only if it is always set. (Check it is always bigger than the motor resolution).

Source: from sprint demo 24/4/2019