Reverse logFormatText bool flag

[guunergooner]

• log_format_text: 日志的输出格式，json或者plaintext，true会输出成json格式，false会输出成非json格式

• code review

	var logInfo string
	for _, sink := range l.sinks {
		if l.logFormatText {
			levelstr := FormatLogLevel(log.LogLevel)
			extraData, ok := log.Data["error"].(string)
			if ok && extraData != "" {
				extraData = " error: " + extraData
			}
			logInfo = log.Timestamp + " " + levelstr + " " + log.File + " " + log.Message + extraData
			sink.Log(loglevel, []byte(logInfo))

		} else {
			logInfo, jserr := log.ToJSON()
			if jserr != nil {
				fmt.Printf("[lager] ToJSON() ERROR! action: %s, jserr: %s, log: %+v", action, jserr, log)
				// also output json marshal error event to sink
				log.Data = Data{"Data": fmt.Sprint(logData)}
				jsonerrdata, _ := log.ToJSON()
				sink.Log(ERROR, jsonerrdata)
				continue
			}
			sink.Log(loglevel, logInfo)
		}
	}