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!)