.github/workflows: Bump the docker/build-push-action to the v2 version

[timflannagan]

Update the test-scripts.yml workflow and replace the
docker/build-push-action to use the v2 version.

These changes were made by following their upgrade from v1 to v2 guide:

• https://github.com/docker/build-push-action/blob/master/UPGRADE.md.

We only use this action currently to ensure that builds are successful
and don't push (or test against) the newly build container image.

Fixes #2144

Description of the change:

Motivation for the change:

Reviewer Checklist

• Implementation matches the proposed design, or proposal is updated to match implementation
• Sufficient unit test coverage
• Sufficient end-to-end test coverage
• Docs updated or added to /doc
• Commit messages sensible and descriptive

[joelanford]

/lgtm

[kevinrizza]

/approve

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: kevinrizza, timflannagan

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[timflannagan]

/override unit

[openshift-ci]

@timflannagan: /override requires a failed status context or a job name to operate on.
The following unknown contexts were given:

• unit

Only the following contexts were expected:

• tide

In response to this:

/override unit

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[timflannagan]

Manually merging - that unit test is permafailing.

[timflannagan]

#2091