grafana: switch to timeseries

address #730

Change-Id: Idce087155f9c9399d347a6ddbaeae093af542418

Author: rdementi

src/dashboard.cpp

@@ -325,7 +325,7 @@ class GraphPanel : public Panel
         "sort": 0,
         "value_type": "individual"
       },
-      "type": "graph",
+      "type": "timeseries",
       "xaxis": {
         "buckets": null,
         "mode": "time",