feat(graph): refactorings

public/app/plugins/datasource/grafana/datasource.ts

@@ -9,6 +9,8 @@ class GrafanaDatasource {
     return this.backendSrv.get('/api/metrics/test', {
       from: options.range.from.valueOf(),
       to: options.range.to.valueOf(),
+      scenario: 'random_walk',
+      interval: options.intervalMs,
       maxDataPoints: options.maxDataPoints
     });
   }