Honour allowed_scms_use_* kojid options

[tkopecek]

Introduced in koji 1.26 (https://pagure.io/koji/issue/2757)

Maintainers will complete the following section

• [ ] Commit messages are descriptive enough
• [ ] Code coverage from testing does not decrease and new code is covered
• [ ] JSON/YAML configuration changes are updated in the relevant schema
• [ ] Pull request has a link to an osbs-docs PR for user documentation updates

[MartinBasti]

Mocking in tests must be updated, it's failing on AttributeError

[rcerven]

closing this in favor of https://github.com/containerbuildsystem/koji-containerbuild/pull/238