openQA: product-testing please provide a way to inject a custom repository

[lkocman]

We need to be able to change/inject repository for product (e.g. Leap 16) for installation in openQA

We need to be able to test against repositories from the new product build in OBS rather than previously published repo in https://download.opensuse.org/distribution/leap/16.0/repo/oss/.

I understand that we pass the repository as a boot param on Leap 15.

openQA sync's it from OBS with openqa obs sync.