Initialize map before inserting elements

[swetharepakula]

Validation errors are masked because of the following error:

panic: assignment to entry in nil map [recovered]
panic: assignment to entry in nil map

Example run: https://prow.k8s.io/view/gs/kubernetes-jenkins/pr-logs/pull/enhancements/2673/pull-enhancements-verify/1389750336436047872

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

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[ehashman]

/close

duplicate of #2676

[k8s-ci-robot]

@ehashman: Closed this PR.

In response to this:

/close

duplicate of #2676

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