Add missing JSON format for dashboard

Change-Id: I43a6c38f1907b9f8fcef8af6bde8b5c85a41ce8c
diff --git a/neutron/meta/grafana.yml b/neutron/meta/grafana.yml
index a37eef8..ea32f2e 100644
--- a/neutron/meta/grafana.yml
+++ b/neutron/meta/grafana.yml
@@ -1,3 +1,4 @@
 dashboard:
   neutron:
+    format: json
     template: neutron/files/grafana_influxdb.json