Return 2 when certificates are not found during requests
    
    The ipa tool has nearly since epoch returned 2 for the case of
    entry not found.
    
    The certificate processing raises a separate error,
    CertificateOperationsError, when something goes wrong.
    This returns 1.
    
    With the introduction of the JSON API most requests will get
    a proper HTTP return code representing what went wrong. In this
    case we can use 404 to determine if the request resulted in
    a NotFound therefore can eventually return a 2 and be
    consistent in return values.
    
    Related: https://pagure.io/freeipa/issue/9562
    
    Signed-off-by: Rob Crittenden <rcritten@redhat.com>
    Reviewed-By: Florence Blanc-Renaud <flo@redhat.com>