Add juno compat jobs to the tempest check pipeline

Now that Juno has been released we need to run every tempest commit
against juno to verify that a commit to tempest master doesn't break
running against the new stable branch. This commit adds these jobs.
However, until all the machinery is in place for grenade we can't run
it against stable/juno, so those jobs are missing.

Change-Id: I4835c321bb22eaadc0d9fe282a0004ba00019ffa
Merge "Add juno compat jobs to the tempest check pipeline"