Use single snapshot to reduce build times

[iancoffey]

What this PR does / why we need it:

I have noticed that, when building with the cluster resource with large image layers, the multiple snapshots that are taken can add a lot amount of time to the build. You will see these as the Taking snapshot of full filesystem... logs in the builder logs.

Using a single snapshot at the end of the process should shave quite a bit of time off the build/

Special notes for your reviewer:

1. Please confirm that if this PR changes any image versions, then that's the sole change this PR makes.

Release note:

Reduce cluster build time with Kaniko by making use of "--single-snapshot" ability of executor.

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[kubeflow-bot]

This change is 

[k8s-ci-robot]

Hi @iancoffey. Thanks for your PR.

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[iancoffey]

@googlebot I fixed it

[iancoffey]

/assign @karthikv2k

[iancoffey]

@googlebot I fixed it

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[googlebot]

CLAs look good, thanks!

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[jinchihe]

/ok-to-test

[jinchihe]

/lgtm /approve

Thanks @iancoffey

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: jinchihe

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