IMAT: Motor Shutdown investigation

On 29/09/2020 a call came in causing https://github.com/ISISComputingGroup/IBEX/issues/5767. The further concerns outlined on this ticket should be investigated in the shutdown, these are:

- We observed that the motor value and setpoint did not stay at the original setpoint for long after being initially set they tended to move around quite close to the original setpoint but sometimes as far as 2 degrees out.
- The motor and encoder values drifted quite a lot after moves.
- Homes did not always jog to zero as was expected (however they did get to a repeatable value)