Merge pull request #28213 from Random-Liu/docker-validation-node-e2e

Automatic merge from submit-queue

Node E2E: Prep for continuous Docker validation node e2e test

Based on https://github.com/kubernetes/kubernetes/pull/28516, for https://github.com/kubernetes/kubernetes/issues/25215.

https://github.com/kubernetes/kubernetes/pull/26813 added support to run e2e test on gci preview image and newest docker version.
This PR added the same support to node e2e test.

The main dependencies of node e2e test are `docker`, `kubelet`, `etcd` and `apiserver`.
Currently, node e2e test builds `kubelet` and `apiserver` locally, and copies them into `/tmp` directory in VM instance. GCI also has built-in `docker`. So the only dependency missing is `etcd`.

This PR injected a simple cloud-init script when creating instance to install `etcd` during node startup.

@andyzheng0831 for the cloud init script.
@wonderfly for the gci instance setup.
@pwittrock for the node e2e test change.

/cc @dchen1107 

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hack/verify-flags/known-flags.txt

@@ -214,6 +214,7 @@ input-dirs
 insecure-bind-address
 insecure-port
 insecure-skip-tls-verify
+instance-metadata
 instance-name-prefix
 iptables-masquerade-bit
 iptables-sync-period