infra/clusters: upgrade terraform to 0.15 for all but k8s-infra-public-pii#2210

k8s-ci-robot merged 2 commits intokubernetes:mainkubernetes/k8s.io:mainfrom

spiffxp:terraform-v0.15spiffxp/k8s.io:terraform-v0.15Copy head branch name to clipboard