Revert "Revert "Drop support for --gce-service-account, require activated creds""

hack/ginkgo-e2e.sh

@@ -121,7 +121,6 @@ export PATH=$(dirname "${e2e_test}"):"${PATH}"
   --provider="${KUBERNETES_PROVIDER}" \
   --gce-project="${PROJECT:-}" \
   --gce-zone="${ZONE:-}" \
-  --gce-service-account="${GCE_SERVICE_ACCOUNT:-}" \
   --gke-cluster="${CLUSTER_NAME:-}" \
   --kube-master="${KUBE_MASTER:-}" \
   --cluster-tag="${CLUSTER_ID:-}" \

hack/jenkins/e2e-runner.sh

@@ -247,7 +247,6 @@ fi
 if [[ -f "${KUBEKINS_SERVICE_ACCOUNT_FILE:-}" ]]; then
   echo 'Activating service account...'  # No harm in doing this multiple times.
   gcloud auth activate-service-account --key-file="${KUBEKINS_SERVICE_ACCOUNT_FILE}"
-  unset GCE_SERVICE_ACCOUNT  # Use checked in credentials, not the metadata server
   unset KUBEKINS_SERVICE_ACCOUNT_FILE
 elif [[ -n "${KUBEKINS_SERVICE_ACCOUNT_FILE:-}" ]]; then
   echo "ERROR: cannot access service account file at: ${KUBEKINS_SERVICE_ACCOUNT_FILE}"