Group by scenario as well when deciding 'obsolete' waivers (#68)
    
    Otherwise waivers for *different* scenarios will obsolete each

    other. This is why waiving cases of the same test with different

    scenarios from Bodhi isn't working right at the moment, I think.

    e.g. if you have an update which is gated on both

    update.install_default_update_live for scenario

    fedora.updates-kde-live-iso.x86_64.64bit and

    update.install_default_update_live for scenario

    fedora.updates-kde-live-iso.x86_64.uefi , and you hit the Waive

    button in Bodhi, Bodhi will correctly issue waivers for both

    scenarios, but waiverdb will immediately decide that whichever

    gets created second obsoletes the one that got created first.

    You can never get waivers for both to be 'current' at the same

    time.

    

    This also adds a test to ensure that the include_obsolete=0

    query parameter works as intended, because if that is broken, the

    test for the "different scenario" case might pass when it should

    not.

    

    Signed-off-by: Adam Williamson <awilliam@redhat.com>