fix green untested links, non-arch weights, openqa dupes
    
    three bug fixes that showed up during testing of the failed
    test link stuff.
    
    A cut/paste error in the new get_cell() meant untested links
    were green instead of blue.
    
    The image groups are sorted by a weight calculation done by
    fedfind. This took arch into account. This was a problem,
    because for nightlies the image groups include images of many
    arches, so the weight was somewhat unpredictable: nightlies
    just picks some random image (the first in the list for the
    group) to do the weight score with, and if it happened to pick
    an ARM image for a group that includes ARM images, that group
    would be heavily penalized. This is why the 'Server DVD' group
    would sometimes show up way down the list. So in fedfind 2.4.5
    I made it possible to tell fedfind to ignore the arch, and now
    we do that (and the weight is calculated solely from the sub
    variant).
    
    update_openqa() didn't check for dupes, so if you call it more
    than once on the same compose it would add duplicates of
    already-stored job dicts. This wasn't obviously visible before
    but with the links, it was pretty clear. So this is fixed from
    two ends: update_openqa() now won't add a job if it's already
    in the list (I hope python's 'dict in list' is up to this...),
    and prune_jobs checks through the list of openqa jobs for ones
    with the same job ID and removes dupes.