Added OpenTSDB nested templating fix to CHANGELOG

CHANGELOG.md

@@ -30,6 +30,7 @@
 * **Elasticsearch**: Fix for query template variable when looking up terms without query, no longer relies on elasticsearch default field, fixes [#3887](https://github.com/grafana/grafana/pull/3887)
 * **Elasticsearch**: Fix for displaying IP address used in terms aggregations, fixes [#4393](https://github.com/grafana/grafana/pull/4393)
 * **PNG Rendering**: Fix for server side rendering when using auth proxy, fixes [#5906](https://github.com/grafana/grafana/pull/5906)
+* **OpenTSDB**: Fixed multi-value nested templating for opentsdb, fixes [#6455](https://github.com/grafana/grafana/pull/6455)
 
 # 3.1.2 (unreleased)
 * **Templating**: Fixed issue when combining row & panel repeats, fixes [#5790](https://github.com/grafana/grafana/issues/5790)