Ticket 48184 - close connections at shutdown cleanly.
    
    Bug Description:  During shutdown we would not close connections.
    In the past this may have just been an annoyance, but now with the way
    nunc-stans works, io events can still trigger on open xeisting connectinos
    during shutdown.
    
    Fix Description:  Close connections during shutdown rather than
    leaving them alive.
    
    https://pagure.io/389-ds-base/issue/48184
    
    Author: wibrown
    
    Review by: lkrispen, vashirov (Thank you!)