IOC: McLennan has a don't home behaviour

As a TOSCA instrument scientist, I want the sample changer not to have a homing routine defined, so it doesn't accidentally home.

On TOSCA, a McLennan is used to drive the sample changer which is used to move some steps at a time. The homing mode in LabView is set up to home to the current position, i.e. not home at all. This ticket replicates this behaviour in the McLennan driver.

This ticket requires the addition of a new state to the SNL sequencer that controls the homing behaviour of the motor.

This new state is essentially a "no-op" homing routine.