Right now, the buildslave roles assume that there will only be one buildslave per host. As we start to deploy the disposable clients, we will want to have multiple buildslaves per host.

Refactor the current taskotron/buildslave and taskotron/buildslave-configure roles so that we can specify multiple buildslaves with slightly different configuration on hosts. Try not to make this too taskotron-specific if that's sanely possible - the docs folks are looking to start using buildbot soon and it would be nice if they could reuse the roles that we've written instead of having to create and maintain their own.