Not to log class name

[yaojingguo]

Now, the log message contains the class name: 2021-12-19 22:59:31,787 ERROR [main] org.fluentd.logger.sender.RawSocketSender java.net.ConnectException: Connection refused (Connection refused)

Since log frameworks usually have a way to log class name without the need to include it in the log message, the class name should be removed. The following text shows a sample log mesage after this change:

2021-12-19 22:56:58,842 ERROR [main] flush failed java.net.ConnectException: Connection refused (Connection refused)