Add new line protocol parser and serializer, influxdb output (#3924)

plugins/serializers/json/json.go

@@ -22,7 +22,7 @@ func (s *JsonSerializer) Serialize(metric telegraf.Metric) ([]byte, error) {
 	m["tags"] = metric.Tags()
 	m["fields"] = metric.Fields()
 	m["name"] = metric.Name()
-	m["timestamp"] = metric.UnixNano() / units_nanoseconds
+	m["timestamp"] = metric.Time().UnixNano() / units_nanoseconds
 	serialized, err := ejson.Marshal(m)
 	if err != nil {
 		return []byte{}, err