Make LLUDPServer.Scene publicly gettable/privately settable instead of protected so that other logging code in the clientstack can record more useful information

Adds some commented out logging for use again in the future.
No functional change.

OpenSim/Region/ClientStack/Linden/UDP/LLUDPClient.cs

@@ -672,6 +672,8 @@ namespace OpenSim.Region.ClientStack.LindenUDP
         /// signature</param>
         private void FireQueueEmpty(object o)
         {
+//            m_log.DebugFormat("[LLUDPCLIENT]: FireQueueEmpty for {0} in {1}", AgentID, m_udpServer.Scene.Name);
+
 //            int start = Environment.TickCount & Int32.MaxValue;
 //            const int MIN_CALLBACK_MS = 30;