[INFRA-102] enable mirrorbrain module

It turns out that the whole mirrorbrain module was not actively used.

In looking at this module, I think @rtyler worked on this some time ago when he was trying to move this off to lettuce, until that idea got scrapped (for having @aheritier use this machine to run JIRA.)

In this pull request I'm enabling this back to manage mirrorbrain as it currently runs on cucumber. 

The following log shows the result of `puppet apply --modulepath=modules --verbose --noop -e "include mirrorbrain"` dry-run result: https://gist.github.com/kohsuke/abb0f0c6f7168dc3c6ca

I vetted each line of changes and ensured they are OK.