Fix session takeover.

Source/MQTTnet/Server/MqttServer.cs

@@ -148,7 +148,7 @@ namespace MQTTnet.Server
 
         private void OnClientAccepted(object sender, MqttServerAdapterClientAcceptedEventArgs eventArgs)
         {
-            eventArgs.SessionTask = _clientSessionsManager.StartSession(eventArgs.Client);
+            eventArgs.SessionTask = _clientSessionsManager.HandleConnectionAsync(eventArgs.Client);
         }
     }
 }