Add distinction between 404 and 500 for external collaborator access

While testing the sync script with the new profile-api locally, a gap was discovered.

When syncing project team access, there is a check to ensure a 500 from a back-end process is handled differently than a 404. This ensures people aren't assumed to be invalid team members when there is something wrong with the profile-api.

There is currently no such logic for external collaborators. Reusing the logic mentioned above, with sufficient logging, should cover this case.