Ticket 49289 - Improve result handling from connections with NS
    
    Bug Description:  In debug builds with replication it was noticed that
    we aren't closing connections at shutdown. This has always been the case
    but now with nunc-stans we are seeing it. To make it worse, in a debug
    build this would trigger an assertion that caused the server to
    abrt().
    
    Fix Description:  Change the result return type from nunc-stans from
    simple "true false",to an enum, that allows us to detect more conditions
    and make informed decisions as a caller. In the future we need to close
    connections at shutdown, but this requires much more work around the
    connection process and has been delayed for 1.4.0.
    
    See also: https://pagure.io/389-ds-base/issue/48184
    
    https://pagure.io/389-ds-base/issue/49289
    
    Author: wibrown
    
    Review by: tbordaz (Thanks!)