Add us-central1-b, us-central1-c into additional_zones of gke-cluster module
Add us-central1-b, us-central1-c into additional_zones of gke-cluster module

mrtyler/gpii-infra,mrtyler/gpii-terraform,mrtyler/gpii-infra,mrtyler/gpii-infra,mrtyler/gpii-terraform,mrtyler/gpii-infra,mrtyler/gpii-terraform