Dockerfile optimization

[alekseyolg]

What type of PR is this?

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespaces from that line:

/kind cleanup

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

Reducing the number of layers, increasing readability, reducing the size of the image (how much I can’t check, it’s impossible for me to build due to the unavailability of the vagrant repository)

[k8s-ci-robot]

Hi @alekseyolg. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[mzaian]

/ok-to-test

[mzaian]

Thanks @alekseyolg
My calculation could tell that this saves 157.4 mb :)

/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: alekseyolg, floryut

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[floryut]

@alekseyolg Thank you for the PR 👍