Dashboard::ProjectsController#index experiences very poor performance

We see very high spikes in latencies on this endpoint. So high in fact that it gets killed off and not logged or recorded in metrics.

The best way to see this behaviour is by looking at Workhorse.

This comes from the investigation taking place on gitlab-com/gl-infra/scalability#64

https://log.gitlab.net/goto/ca9d3cc73a9235cd0580b902a4945d49