fix(circle-ci): change to ubuntu 14 for CI

circle.yml

@@ -31,4 +31,4 @@ deployment:
     branch: master
     owner: grafana
     commands:
-      - ./trigger_grafana_packer.sh ${TRIGGER_GRAFANA_PACKER_CIRCLECI_TOKEN}
+      - ./trigger_grafana_packer.sh ${TRIGGER_GRAFANA_PACKER_CIRCLECI_TOKEN}