fix for incompatible address on restart (#186)

Previously when a listener would restart because of an error while on
an IPv6 address it would give an error ‘An address incompatible with
the requested protocol was used’. This fixes the issue.

src/Fleck/WebSocketServer.cs

@@ -107,7 +107,7 @@ private void ListenForClients()
                     try
                     {
                         ListenerSocket.Dispose();
-                        var socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.IP);
+                        var socket = new Socket(_locationIP.AddressFamily, SocketType.Stream, ProtocolType.IP);
                         ListenerSocket = new SocketWrapper(socket);
                         Start(_config);
                         FleckLog.Info("Listener socket restarted");