Add a job to verify all slaves will boot up

[pcarney8]

Mentioned in the rht-labs/labs-ci-cd meetup, we need to verify all jenkins-slaves will boot up with our instance of Jenkins that we use for labs-ci-cd.

I would like to propose that we do that here, since this is the Jenkins configuration for the rht-labs instance of Jenkins.

@springdo what'd you think? It would be separate from the CI setup for containers-quickstarts

@etsauer and I had discussed where the s2i-config would live for all of the jenkins bits in containers-quickstarts which is a challenge because of the inception loops there.

But IMO I think this is the place that we add the job of booting up all the slave instances. similar to your multi-branch. It then wouldn't be inception looping in the labs-ci-cd repo.