webui tests: fix test_subid suite
    
    The webui test test_subid_range_deletion_not_allowed is
    adding a new subid for the admin user but a previous
    test already took care of that step.
    Remove the call adding the subid.
    
    2nd issue: a given record has to be selected in
    order to check that there is no "delete" button.
    
    Fixes: https://pagure.io/freeipa/issue/9214
    
    Signed-off-by: Florence Blanc-Renaud <flo@redhat.com>
    Reviewed-By: Rob Crittenden <rcritten@redhat.com>