Add tests for Random Serial Number v3 support
    
    Extend existing tests and enabled random serial numbers
    during installation. A subset of tests was identified that
    exercise the code sufficiently to ensure proper operation.
    
    Update the xml-rpc test to allow the new RSN version number
    attribute.
    
    Update some certificate tests where a specifc serial number
    is expected.
    
    Fixes: https://pagure.io/freeipa/issue/2016
    
    Signed-off-by: Rob Crittenden <rcritten@redhat.com>
    Reviewed-By: Florence Blanc-Renaud <flo@redhat.com>
    Reviewed-By: Francisco Trivino <ftrivino@redhat.com>
    Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>