When linking issues or creating sub-tasks under parent issues via csv import, Issue Id value is saved to External issue ID field

I only recently realized that this functionality is actually a bug, and does not seem to be intended functionality.

When using the admin level CSV import function the value in the "Issue Id" field is being saved to the External Issue ID field. This means that unless you remove this value post-creation by editing issues, the next time you use the same value in the "Issue Id" for a CSV import, it is not treated as a new issue but an existing one, and is not created. Any sub-tasks being created are now under the old issue instead of a new one, and any issues being linked are now linked to the old issue instead of a new one.

This only occurs with admin level CSV import, and does not occur with the new non-admin bulk create issue functionality.