fix: [stix2 import] Fixed parsing of objects mapped into galaxies for external STIX
fix: [stix2 import] Fixed parsing of objects mapped into galaxies for external STIX

- Mapping dictionary was not loaded correctly
  while calling the ExternalStixParser class, and
  it is now fixed
- For objects from external STIX content that
  should be mapped as galaxies (such as malware,
  threat actor, and so on), we do not only test
  the perfect match with one of the galaxy names
  in the mapping dictionary, we also test now if
  the galaxy name is contained in any of the
  known galaxy names of the dictionary

MISP/MISP,MISP/MISP,MISP/MISP,SteveClement/MISP,MISP/MISP,SteveClement/MISP,MISP/MISP,SteveClement/MISP,SteveClement/MISP,SteveClement/MISP