conf: Drop unnecessary caps parsing logic
    
    The comment says:
    
        /* If the logic here seems fairly arbitrary, that's because it is :)
         * This is duplicating how the code worked before
         * CapabilitiesDomainDataLookup was added. We can simplify this,
         * but it would take a bit of work because the test suite fails
         * in numerous minor ways. */
    
    Nowadays the test suite changes appear quite simple, just extending
    test capabilities data a bit so that we aren't trying to define
    invalid arch/os/virtType/machine combos
    
    Acked-by: Michal Privoznik <mprivozn@redhat.com>
    Signed-off-by: Cole Robinson <crobinso@redhat.com>