Added callback to retrieve response data, otherwise socket won't set to free.
Added callback to retrieve response data, otherwise socket won't set to free.

mallocator/Elasticsearch-Exporter,xeeo/Elasticsearch-Exporter,deseretbook/elasticsearch-exporter,ankon/Elasticsearch-Exporter,vtrifonov/Elasticsearch-Exporter,ankon/Elasticsearch-Exporter,deseretbook/elasticsearch-exporter,mallocator/Elasticsearch-Exporter,vtrifonov/Elasticsearch-Exporter,xeeo/Elasticsearch-Exporter