Enable setting proxy for user-data

[gyliu513]

/kind bug

What steps did you take and what happened:
[A clear and concise description of what the bug is.]

I'm now proposing this for Cluster API use case at kubernetes-sigs/cluster-api#903 (comment)

This is mainly used to handle the case where my VM cannot access external internet without a proxy.

[jichenjc]

will this cover the use case that deployed VM can't access internet at all so have to use internal stuff? or just proxy (NAT? ) the request through proxy server?

[fejta-bot]

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/lifecycle stale

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/lifecycle rotten

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/close

[k8s-ci-robot]

@fejta-bot: Closing this issue.

In response to this:

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