Greenwave: separate upgrade tests in openQA update gating policy
    
    The upgrade tests are not run on updates for the oldest stable
    release, because we don't want to maintain base images for EOL
    releases. So we can't gate the oldest stable release (currently
    F34) on those tests as we don't run them. To handle this let's
    split the policy in two and have the policy for the upgrade tests
    apply only to the release(s) they're actually run on.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>