Honor image type option in GKE cluster deploy

[saikat-royc]

What type of PR is this?

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/kind api-change
/kind bug
/kind cleanup
/kind design
/kind documentation
/kind failing-test
/kind feature
/kind flake

What this PR does / why we need it:
Honor image-type in GKE cluster deploy. (Fix the bug introduced in #515)

Which issue(s) this PR fixes:

Fixes #535

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

Honor image-type in GKE cluster deploy

[k8s-ci-robot]

Hi @saikat-royc. 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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[saikat-royc]

/assign @msau42 @mattcary

[k8s-ci-robot]

@saikat-royc: GitHub didn't allow me to assign the following users: mattcary.

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/assign @msau42 @mattcary

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[msau42]

/ok-to-test
/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: msau42, saikat-royc

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