(WIP, not tested) Clean up repo checks

Checking for the optional product identifier is wrong. Seems
like there was a repoid added for this purpose, so lets use that.
It seems I get this:
```
gpg: Signature made Wed Oct 23 18:03:30 2013 CEST using RSA key ID 307E3D54
gpg: [don't know]: invalid packet (ctb=2d)
gpg: keydb_search failed: Invalid packet
gpg: Can't check signature: No public key
```