Issue 49329 - Descriptive error msg for USN cleanup task
    
    Bug Description: Providing either a suffix or backend attribute is necessary
    in order for a USN tombstone cleanup task entry to be created, otherwise
    the server will not accept the operation. However in this case it just
    returns a generic error message which is not helpful for adressing the
    issue; "Bad parameter to an ldap routine (-9)".
    
    Fix Description: Provide an additional descriptive message in this case.
    
    https://pagure.io/389-ds-base/issue/49329
    
    Author: Ilias95
    
    Review by: wibrown (thanks for this!)