add cookie log message for debugging

Author: mischa

kcp2k/kcp2k/highlevel/KcpPeer.cs

@@ -113,6 +113,7 @@ protected KcpPeer(KcpConfig config, uint cookie)
             // set the cookie after resetting state so it's not overwritten again.
             // with log message for debugging in case of cookie issues.
             this.cookie = cookie;
+            Log.Info($"{GetType()}: created with cookie={cookie}");
 
             // create mtu sized send buffer
             rawSendBuffer = new byte[config.Mtu];