New CI integration request: OpenLab

Hi everyone!

The OpenStack cloud plugin is quite valuable in both the Jenkins and the OpenStack ecosystem because it allows for the use of one-use slaves which has many advantages, the plugin has a fairly reliant userbase as well.

Unfortunately, there does not seem to be any gating against OpenStack for this and testing is mostly done by manual work against clouds deployed by reviewers. This probably slows down review and makes it much harder to make sure things are running properly.

[OpenLab](https://openlabtesting.org/) uses donated infrastructure from several public cloud providers (including us!) to test ecosystem applications. I'd like to ask if the project would be interested in having it tested by OpenLab.

My ideal goal would be to deploy OpenStack via DevStack and run all the tests against it for every pull request, this will significantly facilitate testing and make it easier to do contributors without worrying about breaking anything.

If this is something that interests the team, we would need 2 main things:

1) A webhook must be installed in order to notify the Zuul CI system to trigger builds
2) A `.zuul.yaml` file will be added to the repo which contains all job definitions.

I can personally pick up the work to get the jobs done if need be, but I think this would be a great option that would hopefully increase the stability of the project.

Thank you!