Prevent the creation on users and groups with numeric characters only
    
    Update regular expression validator to prevent user and group creation.
    
    Fixes: https://pagure.io/freeipa/issue/7572
    
    Signed-off-by: Armando Neto <abiagion@redhat.com>
    Reviewed-By: Rob Crittenden <rcritten@redhat.com>