logging: fix GKE resource autodetection

[freelerobot]

GKE was:

resource: {
  type: "gce_instance"
  labels: {
    project_id: "log-bench"
    zone: "us-west1-a"
    instance_id: "4837119632664073093"
  }
}

Should be:

resource: {
  type: "k8s_container"
  labels: {
    pod_name: "go-gke-6969bf5b9d-rwbw8"
    container_name: "hello-app"
    cluster_name: "go-gke"
    namespace_name: "default"
    project_id: "log-bench"
    location: "us-west1-a"
  }
}

[freelerobot]

Available ENVVARS
KUBERNETES_SERVICE_PORT_HTTPS=443
KUBERNETES_SERVICE_PORT=443
HOSTNAME=log-go-gke-nicolezhx-6ccbd9769f-l2v46
PWD=/
ENABLE_SUBSCRIBER=true
HOME=/root
KUBERNETES_PORT_443_TCP=tcp://10.3.240.1:443
TERM=xterm
SHLVL=1
KUBERNETES_PORT_443_TCP_PROTO=tcp
KUBERNETES_PORT_443_TCP_ADDR=10.3.240.1
KUBERNETES_SERVICE_HOST=10.3.240.1
KUBERNETES_PORT=tcp://10.3.240.1:443
KUBERNETES_PORT_443_TCP_PORT=443
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
PUBSUB_TOPIC=log-go-gke-nicolezhx
_=/usr/bin/printenv

———————————
Available metadata/attributes:
cluster-location
cluster-name
cluster-uid
configure-sh
created-by
disable-legacy-endpoints
enable-oslogin
gci-ensure-gke-docker
gci-metrics-enabled
gci-update-strategy
google-compute-enable-pcid
instance-template
kube-env
kube-labels
kubeconfig
kubelet-config
serial-port-logging-enable
user-data