Flint: scatter regular do not warn if start/stop is not specified

Feedback from @homsrego ID13.

The custom beamline scatter was not displayed at the proper location during the scan.

The height is smaller than expected, except at the end.

A work around is to use irregular rendering.

It is probably a problem on the scan info setup. But i was not able to fine it for now.

EH2 [4]: dkmapyz_2(0,0.1,50,0,0.1,50,0.025)

{'axis:ustrz': {'axis-id': 1,
                'axis-kind': 'forth',
                'axis-points': 51,
                'max': -7.581701000000001,
                'min': -7.681701,
                'points': 2601},
 'ustry_position': {'axis-id': 0,
                    'axis-kind': 'forth',
                    'axis-points': 51,
                    'max': -11.581000000000005,
                    'min': -11.681000000000004,
                    'points': 2601}}

{'axis': {'images': [],
          'master': {'images': [], 'scalars': ['axis:ustrz'], 'spectra': []},
          'scalars': ['ustry_position',
                      'umusst_master:timer',
                      'umusst_master:enc_ustry',
                      'ustry_up',
                      'ustry_down',
                      'ustry_mean',
                      'ustry_delta',
                      'p201_eh2_0:ct2_counters_controller:ct21',
                      'p201_eh2_0:ct2_counters_controller:ct22',
                      'p201_eh2_0:ct2_counters_controller:ct23',
                      'p201_eh2_0:ct2_counters_controller:ct24',
                      'p201_eh2_0:ct2_counters_controller:ct25',
                      'p201_eh2_0:ct2_counters_controller:ct26',
                      'p201_eh2_0:ct2_counters_controller:ct27',
                      'p201_eh2_0:ct2_counters_controller:ct28',
                      'p201_eh2_0:ct2_counters_controller:ct29',
                      'p201_eh2_0:ct2_counters_controller:ct2a',
                      'p201_eh2_0:ct2_counters_controller:acq_time_2'],
          'spectra': []}}