asmcli doesn't support internal ip for GKE

[bloodsper]

It feels a bit weird, that the recommend GKE (or any real hardened) setup from Google

isn't supported that well from asmcli, and I'm not sure if this is being avoided with the new fleet api coming in; but it would be nice to be able to add like --internal-ip to asmcli instead of having to modify the script every time I download

e.g.

info "Fetching/writing GCP credentials to kubeconfig file..."
KUBECONFIG="${KUBECONFIG}" retry 2 gcloud container clusters get-credentials "${CLUSTER_NAME}" \
  --project="${PROJECT_ID}" \
  --internal-ip \
  --zone="${CLUSTER_LOCATION}"