Get article path for foreign DB repos too

We have had this method in all Repo subclasses for a while, but sadly
it never got used and we've unintentionally crippled foreign DB repos
for some time now.

{{fixed}}

Change-Id: I972eb739cdd56c666981d5fbc371fa53024ff359
Mingle: https://wikimedia.mingle.thoughtworks.com/projects/multimedia/cards/217
Merge "Get article path for foreign DB repos too"