`flasharray_client.get_volumes_space` does sometimes return empty items if `start_time` is passed

[b1-luettje]

In [33]: list(fa_client.get_volumes_space().items)
Out[33]:
[{'id': '25b7579e-b931-318e-cc20-9b1ca6ddac5b',
  'name': 'vg0/vol0',
  'space': {'data_reduction': 5.500982707812342,
            'snapshots': 0,
            'thin_provisioning': 0.9979329109191895,
            'total_physical': 403477,
            'total_provisioned': 1073741824,
            'total_reduction': 2661.2218887321956,
            'unique': 403477,
            'virtual': 2219520},
  'time': 1629446265839},
 {'id': 'f33edf36-a534-92da-6411-90e96edc91b4',
  'name': 'vg0/vol1',
  'space': {'data_reduction': 1.2885002872516937,
            'snapshots': 0,
            'thin_provisioning': 0.9960825824737549,
            'total_physical': 163224255,
            'total_provisioned': 53687091200,
            'total_reduction': 328.91574069377634,
            'unique': 163224255,
            'virtual': 210314752},
  'time': 1629446265839},
 {'id': 'ed419d14-43b4-8b8c-6a50-262cb0afb847',
  'name': 'vg0/vol3',
  'space': {'data_reduction': 2.127529711123683,
            'snapshots': 0,
            'thin_provisioning': 0.7472276592254639,
            'total_physical': 6372867159,
            'total_provisioned': 53687091200,
            'total_reduction': 8.416782091761233,
            'unique': 6372867159,
            'virtual': 13570611712},
  'time': 1629446265839}]

In [34]: list(fa_client.get_volumes_space(start_time=1629446285292).items)  # missing response items
Out[34]: []

In [35]: list(fa_client.get_volumes_space(start_time=1629446284292).items)  # only 1000 ms earlier than the previous request
Out[35]:
[{'id': '25b7579e-b931-318e-cc20-9b1ca6ddac5b',
  'name': 'vg0/vol0',
  'space': {'data_reduction': 5.500982707812342,
            'snapshots': 0,
            'total_physical': 403477,
            'total_provisioned': 1073741824,
            'unique': 403477},
  'time': 1629446314000},
 {'id': 'f33edf36-a534-92da-6411-90e96edc91b4',
  'name': 'vg0/vol1',
  'space': {'data_reduction': 1.3277077908386596,
            'snapshots': 0,
            'total_physical': 158086222,
            'total_provisioned': 53687091200,
            'unique': 158086222},
  'time': 1629446314000},
 {'id': 'ed419d14-43b4-8b8c-6a50-262cb0afb847',
  'name': 'vg0/vol3',
  'space': {'data_reduction': 2.1326029279724117,
            'snapshots': 0,
            'total_physical': 6365880525,
            'total_provisioned': 53687091200,
            'unique': 6365880525},
  'time': 1629446314000}]

In [36]: fa_client.get_rest_version()
Out[36]: '2.7'