Galils: restore defaults if autosave file is corrupt when loading at startup

Following on from the discussion in #6170

The notes in https://github.com/ISISComputingGroup/IBEX/issues/6170#issuecomment-781273960 should give an idea of how implementing this could work

### Acceptance criteria
- When galil autosave files are corrupt or not able to be loaded the motor should come up in a state where it cannot be moved
- The user should be clearly warned about this condition and asked to inform us or the IS
- Simulated motors should not come up in this state when autosave is corrupt

### Notes

@FreddieAkeroyd said there is an autosave flag which indicates whether the autosave has been restored, this may give us more information that just a warning message which is overwritten (although you might need to think about what happens over multiple retsarts, or do we assume the user will sort something out)