Support Google Provider 2.1.0

[robmorgan]

I had to lock the Google provider to 2.0.0. 2.1.0 seems to drop the subnetwork self_link. hashicorp/terraform-provider-google#3040

module.gke_cluster.google_container_cluster.cluster: Resource 'data.google_compute_subnetwork.gke_subnetwork' does not have attribute 'self_link' for variable 'data.google_compute_subnetwork.gke_subnetwork.self_link'

Relevant build: https://circleci.com/gh/gruntwork-io/terraform-google-gke/97

@rileykarson am I suppose to use another attribute?

[rileykarson]

Oh yup I accidentally replaced Computed in that datasource's self_link field instead of adding Optional. I'll patch that for our next regular release.

[robmorgan]

@rileykarson Thanks dude!

[autero1]

Think we can close this.