cert: defer cert-find result post-processing
    
    Rather than post-processing the results of each internal search,
    post-process the combined result.
    
    This avoids expensive per-certificate searches when cert-find is executed
    with the --all option on certificates which won't even be included in the
    combined result.
    
    https://pagure.io/freeipa/issue/6808
    
    Reviewed-By: Stanislav Laznicka <slaznick@redhat.com>