docs(): changelog updated

CHANGELOG.md

@@ -18,6 +18,7 @@
 ### Bugfixes
 * **API**: HTTP API for deleting org returning incorrect message for a non-existing org [#6679](https://github.com/grafana/grafana/issues/6679)
 * **Dashboard**: Posting empty dashboard result in corrupted dashboard [#5443](https://github.com/grafana/grafana/issues/5443)
+* **Logging**: Fixed logging level confing issue [#6978](https://github.com/grafana/grafana/issues/6978)
 
 # 4.0.2 (2016-12-08)