Fix rewriting of istio-cni Helm charts in release scripts

[rlenglet]

Rewrite the hub and tag in values_gke.yaml in addition to
values.yaml.

Remove the "git clone ...cni.git" and values.yaml rewriting from
create_charts(), which are redundant with the cloning in
create_release_archives.sh and the rewriting in update_helm().

[ ] Configuration Infrastructure
[ ] Docs
[ ] Installation
[ ] Networking
[ ] Performance and Scalability
[ ] Policies and Telemetry
[ ] Security
[x] Test and Release
[ ] User Experience
[ ] Developer Infrastructure

[rlenglet]

We'll check that the release script still works with the daily release build tonight before backporting to release-1.3.

[rlenglet]

e2e-simpleTestsMinProfile-master failed because KinD couldn't start:

time="23:50:00" level=debug msg="Using kubeadm config:\napiServer:\n  certSANs:\n  - localhost\n  - 127.0.0.1\n  extraArgs:\n    service-account-issuer: kubernetes.default.svc\n    service-account-signing-key-file: /etc/kubernetes/pki/sa.key\napiVersion: kubeadm.k8s.io/v1beta2\nclusterName: istio-testing\ncontrolPlaneEndpoint: 172.17.0.2:6443\ncontrollerManager:\n  extraArgs:\n    enable-hostpath-provisioner: \"true\"\nkind: ClusterConfiguration\nkubernetesVersion: v1.15.0\nname: config\nnetworking:\n  podSubnet: 10.244.0.0/16\n  serviceSubnet: 10.96.0.0/12\nscheduler:\n  extraArgs: null\n---\napiVersion: kubeadm.k8s.io/v1beta2\nbootstrapTokens:\n- token: abcdef.0123456789abcdef\nkind: InitConfiguration\nlocalAPIEndpoint:\n  advertiseAddress: 172.17.0.2\n  bindPort: 6443\nnodeRegistration:\n  criSocket: /run/containerd/containerd.sock\n  kubeletExtraArgs:\n    fail-swap-on: \"false\"\n    node-ip: 172.17.0.2\n---\napiVersion: kubeadm.k8s.io/v1beta2\ncontrolPlane:\n  localAPIEndpoint:\n    advertiseAddress: 172.17.0.2\n    bindPort: 6443\ndiscovery:\n  bootstrapToken:\n    apiServerEndpoint: 172.17.0.2:6443\n    token: abcdef.0123456789abcdef\n    unsafeSkipCAVerification: true\nkind: JoinConfiguration\nnodeRegistration:\n  criSocket: /run/containerd/containerd.sock\n  kubeletExtraArgs:\n    fail-swap-on: \"false\"\n    node-ip: 172.17.0.2\n---\napiVersion: kubelet.config.k8s.io/v1beta1\nevictionHard:\n  imagefs.available: 0%\n  nodefs.available: 0%\n  nodefs.inodesFree: 0%\nimageGCHighThresholdPercent: 100\nkind: KubeletConfiguration\n---\napiVersion: kubeproxy.config.k8s.io/v1alpha1\nkind: KubeProxyConfiguration\n"
time="23:50:00" level=debug msg="Running: /usr/bin/docker [docker exec --privileged istio-testing-control-plane mkdir -p /kind]"
time="23:50:00" level=error msg="failed with:"
time="23:50:00" level=error msg="OCI runtime exec failed: exec failed: container_linux.go:348: starting container process caused \"process_linux.go:90: adding pid 961 to cgroups caused \\\"failed to write 961 to cgroup.procs: write /sys/fs/cgroup/cpu,cpuacct/docker/89232e6ecb5ad5e7470f70cfaa737a3c333e3b55ae43e7310b4c6c69c5ab7065/cgroup.procs: invalid argument\\\"\": unknown"
 ✗ Creating kubeadm config 📜
Error: failed to create cluster: failed to copy kubeadm config to node: failed to create directory /kind/kubeadm.conf: exit status 126
+ echo 'Could not setup KinD environment. Something wrong with KinD setup. Exporting logs.'

[rlenglet]

/test e2e-simpleTestsMinProfile-master

[rlenglet]

/cherrypick release-1.3

[istio-testing]

@rlenglet: new pull request created: #16524

In response to this:

/cherrypick release-1.3

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