changelog: add notes about closing issue

https://github.com/grafana/grafana-docker/issues/170
[skip ci]

CHANGELOG.md

@@ -32,6 +32,7 @@
 
 * **Dashboard**: Dashboard link doesn't work when "As dropdown" option is checked [#12315](https://github.com/grafana/grafana/issues/12315)
 * **Dashboard**: Fix regressions after save modal changes, including adhoc template issues [#12240](https://github.com/grafana/grafana/issues/12240)
+* **Docker**: Config keys ending with _FILE are not respected [#170](https://github.com/grafana/grafana-docker/issues/170)
 
 # 5.2.0-beta1 (2018-06-05)