Fix sending tags over Kafka (#163)

Author: awegrzyn

src/Backends/Kafka.cxx

@@ -77,11 +77,7 @@ void Kafka::send(const Metric& metric)
 
 void Kafka::addGlobalTag(std::string_view name, std::string_view value)
 {
-  std::string sName = name.data();
-  std::string sValue = value.data();
-  if (!tagSet.empty())
-    tagSet += ",";
-  tagSet += sName + "=" + sValue;
+  mInfluxDB.addGlobalTag(name, value);
 }
 
 } // namespace backends

src/Backends/Kafka.h

@@ -59,7 +59,6 @@ class Kafka final : public Backend
 
  private:
   RdKafka::Producer* producer; ///< Kafka producer instance
-  std::string tagSet;          ///< Global tagset (common for each metric)
   InfluxDB mInfluxDB;          ///< InfluxDB instance
   std::string mTopic;          ///< Kafka topic
 };