## Bug description

When going to instance status > internal metrics and refreshing the dashboard, the loading fails

https://user-images.githubusercontent.com/148820/120655500-693c7480-c48b-11eb-8c75-6afd4c967506.mp4

## Expected behavior

It reloads successfully

## How to reproduce

See above

## Environment

- [x] PostHog Cloud
- [x] self-hosted PostHog, version/commit: latest

## Additional context

Seems the cause is that "refresh" requests data from `/api/insight/trends` vs getting it from `/api/dashboard/id` as on first load.

Relates to #3609  

#### *Thank you* for your bug report – we love squashing them!

posthog/api/test/test_dashboard.py
dashboard = Dashboard.objects.create(team=self.team, name="dashboard")
        filter_dict = {
            "events": [{"id": "$pageview"}],
            "properties": [{"key": "$browser", "value": "Mac OS X"}],
        }
        with freeze_time("2020-01-04T13:00:01Z"):
            
            DashboardItem.objects.create(
                dashboard=dashboard, filters=Filter(data=filter_dict).to_dict(), team=self.team, last_refresh=now()
            )
        with freeze_time("2020-01-20T13:00:01Z"):
            response = self.client.get("/api/dashboard/%s/" % dashboard.pk).json()
        self.assertEqual(response["items"][0]["result"], None)
        self.assertEqual(response["items"][0]["last_refresh"], None)
    def test_dashboard_endpoints(self):