Ticket 50370 -  CleanAllRUV task crashing during server shutdown
    
    Description:  There is a race condition during server shutdown that
                  can cause the server to crash.  Increment the active
                  thread count for each cleaning task to prevent the plugins
                  from being closed before the thread terminates.
    
    https://pagure.io/389-ds-base/issue/50370
    
    Reviewed by: firstyear(Thanks!)
    
    (cherry picked from commit 7141b8d10382e8dcb8528b57e5226c82506b79b9)