Enforce GCP limit of 64 chars for cluster name in kubetest2 deployer

[dims]

Ran into this https://storage.googleapis.com/kubernetes-jenkins/pr-logs/pull/127005/pull-kubernetes-e2e-gce-disruptive-canary/1829211781348724736/build-log.txt

I0829 17:57:21.198213   74468 new_cluster.go:1454] Cloud Provider ID: "gce"
Error: error populating configuration: error fetching network "e2e-pr127005-pull-kubernetes-e2e-gce-disruptive-canary-k8s-local": googleapi: Error 400: Invalid value for field 'network': 'e2e-pr127005-pull-kubernetes-e2e-gce-disruptive-canary-k8s-local'. Must be a match of regex '[a-z](?:[-a-z0-9]{0,61}[a-z0-9])?|[1-9][0-9]{0,19}', invalid
W0829 17:57:21.625216   15003 state.go:46] failed to run /home/prow/go/src/k8s.io/kubernetes/_rundir/d5760245-a280-4b20-9469-c66a140b00dc/kops get cluster e2e-pr127005.pull-kubernetes-e2e-gce-disruptive-canary.k8s.local -ojson; stderr=Error: cluster not found "e2e-pr127005.pull-kubernetes-e2e-gce-disruptive-canary.k8s.local"
Error: exit status 1

[dims]

/assign @rifelpet @hakman

[k8s-ci-robot]

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