Draft: ci-package-builder: Try to cope with the OBS API flakiness

Try up to 3 times to get the build logs and results and add a delay between retries, in the hope that in the meantime OBS has a chance to get its acts together and can returns us something useful, since at the moment when it is busy it fails to refresh its internal status in a sensible way and leads to the pipeline not finding the results it looks for and being marked as failed when the build actually succeeded.

See for instance the failed pipelines on !169 (merged) and !170 (merged).