Handle repository transfers better

[arkid15r]

The sync process does not support the case when a repo goes from user's space to OWASP space.
https://github.com/izar/pytm/ was transferred and it caused

duplicate key value violates unique constraint "unique_key_owner" DETAIL: Key (key, owner_id)=(pytm, 1) already exists.
due to node_id clashing (it seems so).

These cases are pretty rare but are quite disruptive for syncing logic.