Ticket 49320 - Activating already active role returns error 16
    
    Bug Description:  ns-activate.pl returns error 16 when trying to activate an
                      already active role.
    
    Fix Description:  Check for error 16 (no such attr), and return error 100.
                      Also added a "redirect"otion to the ldapmod function to
                      hide any errors printed to STDERR, so that the script can
                      display its own error message.
    
    https://pagure.io/389-ds-base/issue/49320
    
    Reviewed by: firstyear(Thanks!)
    
    (cherry picked from commit 406084847f29aa44ffd81de746770aeff6b67c61)