fixed underlying connection not closing on ping timeout

src/main/java/com/corundumstudio/socketio/handler/ClientHead.java

@@ -125,7 +125,7 @@ public class ClientHead {
             public void run() {
                 ClientHead client = clientsBox.get(sessionId);
                 if (client != null) {
-                    client.onChannelDisconnect();
+                    client.disconnect();
                     log.debug("{} removed due to ping timeout", sessionId);
                 }
             }