on_disp always 0 when enable_knob_synthesis=false

[skostogl]

1. on_disp is deactivated:
   https://github.com/lhcopt/lhcmask/blob/master/python_examples/run3_collisions_python/000_pymask.py#L377

2. if enable_imperfections is False & enable_knob_synthesis is also False, exec, crossing_restore; is never called and on_disp=0 even though on_disp=1 in config.py

https://github.com/lhcopt/lhcmask/blob/master/python_examples/run3_collisions_python/000_pymask.py#L402

3. At the moment, this is fixed by setting enable_knob_synthesis=True. Best would be to call "mad_track.input('exec, crossing_restore;')" outside of of "if configuration['enable_knob_synthesis']"

https://github.com/lhcopt/lhcmask/blob/master/python_examples/run3_collisions_python/000_pymask.py#L405