Admin imported `Internal` projects should remain `Internal` when `Internal` visibility is restricted

Problem statement

Once https://gitlab.com/gitlab-org/gitlab-ce/issues/64311 is merged and Internal visibility level being restricted in admin settings, when administrator is importing Internal project, it is being marked as Private. This is intended behaviour for users (https://gitlab.com/gitlab-org/gitlab-ce/issues/64311), but not for administrators. Administrators should be allowed to import Internal projects, even if Internal level is restricted.

The reason this is happening is because allowed visibility levels involve users, and the import is happening inside RepositoryImportWorker which is a background job, there is no notion of user.

Proposed solution

One of the potential solution would be to pass user id to RepositoryImportWorker (https://gitlab.com/gitlab-org/gitlab-ce/blob/master/app/workers/repository_import_worker.rb#L9) so that we can find that user within the background job to understand who initiated the import.