Test upgrade of FreeIPA server and client deployment
    
    Summary:
    This adds an upgrade variant of the FreeIPA tests, with only
    the simplest client enrolment (sssd) for now. The server test
    starts from the N-1 release and deploys the domain controller
    role. The client test similarly starts from the N-1 release
    and, when the server is deployed, enrols as a domain client.
    Then the server upgrades itself, while the client waits (as the
    server is its name server). Then the client upgrades itself,
    while the server does some self-checks. The server then waits
    for the client to do its checks before decommissioning itself,
    as usual. So, summary: *deployment* of both server and client
    occurs on N-1, then both are upgraded, then the actual *checks*
    occur on N.
    
    In my testing, this all more or less works, except the role
    decommission step fails. This failure seems to be a genuine one
    so far as I can tell; I intend to file a bug for it soon.
    
    Test Plan:
    Run the new tests, check they work. Run the existing
    FreeIPA tests (both the compose and the update variants), check
    they both behave the same.
    
    Reviewers: jsedlak, jskladan
    
    Reviewed By: jsedlak
    
    Subscribers: tflink
    
    Differential Revision: https://phab.qa.fedoraproject.org/D1204