add support for regenerating repositories

[ktdreyer]

When setting up an entirely new build tag and target, it's a good idea to generate the repositories for the first time with the koji regen-repo command.

I'm thinking of a new koji_repo module, like:

  handlers:
    - name: regenerate ktdreyer-el7-build
      koji_repo:
        name: ktdreyer-el7-build
        state: regenerated

We could make this module return the values from getRepo(name) and the task_id as well.

[ktdreyer]

In addition to first-time bootstrapping, It's also important to run a repo regeneration any time we change a tag's inheritance.

[ktdreyer]

Returning getRepo is kind of expensive here, and I don't think we'll use it very often. I think we will just return task_id to keep this simple for now.

[ktdreyer]

If a user is running kojira, that seems to kick off almost instantly in my small dev environment. Maybe we should improve any gaps in kojira upstream rather than implementing this.

[ktdreyer]

This would have helped in the internal CLOUDBLD-6000 ticket. I need to investigate whether kojira will kick off when tag inheritance changes.