fix: [stix1 import] Making sure the attribute or object uuid does not raise any issue depending on its type
fix: [stix1 import] Making sure the attribute or object uuid does not raise any issue depending on its type

- Unfortunately the type of the `uuid` field is
  not consistant depending how it has been
  generated: either with the PyMISP class
  `MISPAttribute` / `MISPObject`, or with a
  `MISPEvent.add_attribute` / `MISPEvent.add_object`

MISP/MISP,MISP/MISP,MISP/MISP,MISP/MISP,MISP/MISP