Cluster factories are creating excess records

When creating mock clusters in tests, the cluster factory is creating more records than it needs to.

This looks to be caused by the platform_kubernetes and provider_gcp associations creating their own cluster on top of the one being creating explicitly.

> Clusters::Cluster.count
=> 0
> create(:cluster, :provided_by_gcp);nil
=> nil
> Clusters::Cluster.count
=> 3
> create(:cluster, :provided_by_user);nil
=> nil
> Clusters::Cluster.count
=> 5