Add missing format for the dashboard

Change-Id: Ia56369843208b0fab55431d6ddc13cd5a921833c
diff --git a/cinder/meta/grafana.yml b/cinder/meta/grafana.yml
index e5dc4f9..282fad8 100644
--- a/cinder/meta/grafana.yml
+++ b/cinder/meta/grafana.yml
@@ -1,3 +1,4 @@
 dashboard:
   cinder:
+    format: json
     template: cinder/files/grafana_influxdb.json