## 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, share_token="testtoken", name="public dashboard")
        response = self.client.post(
            "/api/dashboard_item/",
            {
                "dashboard": dashboard.pk,
                "name": "dashboard item",
                "last_refresh": now(),  
            },
        )
        self.assertEqual(response.status_code, status.HTTP_201_CREATED)
        dashboard_item = DashboardItem.objects.get()
        self.assertEqual(dashboard_item.name, "dashboard item")
        
        self.assertRegexpMatches(dashboard_item.short_id, r"[0-9A-Za-z_-]{8}")
    def test_token_auth(self):