Add missing JSON format for dashboard

Change-Id: I405ca58c6e97ab531438340e02ef213e00b0462e
diff --git a/keystone/meta/grafana.yml b/keystone/meta/grafana.yml
index 7e540f4..81ca28b 100644
--- a/keystone/meta/grafana.yml
+++ b/keystone/meta/grafana.yml
@@ -1,3 +1,4 @@
 dashboard:
   keystone:
+    format: json
     template: keystone/files/grafana_influxdb.json