Run usage ping against db replicas

@a_akgun Seeing the first query above, this is related to usage ping. It shows up on the primary workload because it's a sidekiq jobs and those never use replicas so far. I wonder if we could use that as another example for gitlab-com/gl-infra/scalability#566, where we aim to allow sidekiq jobs to use replicas, too. Is it fully read-only on the database?

cc @gitlab-org/growth/product_analytics