add metadata to cos beta images
add metadata to cos beta images

COS beta images have /tmp mounted with 'noexec' mount option.
This makes it impossible for run_remote to execute binaries
from its workspace.
This results in failed kubelet tests, e.g.
ci-kubernetes-node-kubelet-benchmark and
ci-kubernetes-node-kubelet-conformance test suites fail with
"failed to run command './ginkgo': Permission denied" error

Adding metadata pointing to cloud-init(gci-init.yaml) should
solve this as cloud-init remounts /tmp with 'exec' mount option.

pwittrock/test-infra,cjwagner/test-infra,monopole/test-infra,michelle192837/test-infra,cblecker/test-infra,fejta/test-infra,jessfraz/test-infra,fejta/test-infra,brahmaroutu/test-infra,cblecker/test-infra,monopole/test-infra,pwittrock/test-infra,cblecker/test-infra,fejta/test-infra,jessfraz/test-infra,ixdy/kubernetes-test-infra,dims/test-infra,jessfraz/test-infra,brahmaroutu/test-infra,monopole/test-infra,BenTheElder/test-infra,michelle192837/test-infra,cjwagner/test-infra,monopole/test-infra,dims/test-infra,jessfraz/test-infra,fejta/test-infra,cblecker/test-infra,kubernetes/test-infra,kubernetes/test-infra,BenTheElder/test-infra,kubernetes/test-infra,brahmaroutu/test-infra,cjwagner/test-infra,kubernetes/test-infra,ixdy/kubernetes-test-infra,cjwagner/test-infra,cjwagner/test-infra,monopole/test-infra,pwittrock/test-infra,fejta/test-infra,michelle192837/test-infra,dims/test-infra,ixdy/kubernetes-test-infra,michelle192837/test-infra,ixdy/kubernetes-test-infra,cblecker/test-infra,dims/test-infra,pwittrock/test-infra,BenTheElder/test-infra,cblecker/test-infra,monopole/test-infra,BenTheElder/test-infra,jessfraz/test-infra,michelle192837/test-infra,michelle192837/test-infra,ixdy/kubernetes-test-infra,brahmaroutu/test-infra,cjwagner/test-infra,brahmaroutu/test-infra,jessfraz/test-infra,BenTheElder/test-infra,dims/test-infra,dims/test-infra,fejta/test-infra,kubernetes/test-infra,kubernetes/test-infra,pwittrock/test-infra,BenTheElder/test-infra,brahmaroutu/test-infra