Clean up add_repo parameter handling
Clean up add_repo parameter handling

The 3rd parameter can be removed by making everything relative
to CDROOT.

SUSE-Cloud/automation,gosipyan/automation,gosipyan/automation,gosipyan/automation,SUSE-Cloud/automation,aspiers/automation,aspiers/automation,SUSE-Cloud/automation,aspiers/automation,aspiers/automation,SUSE-Cloud/automation,gosipyan/automation