Add DOCKER_BUILDKIT var to fix E2E tests

[Amulyam24]

What this PR does / why we need it:
Add DOCKER_BUILDKIT var to fix E2E tests

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

Special notes for your reviewer:

/area provider/ibmcloud

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

Release note:

This PR adds DOCKER_BUILDKIT var to fix E2E tests

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[mkumatag]

/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Amulyam24, mkumatag

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