NO-JIRA: Update Dockerfile with Immutable Tags

[adambkaplan]

Use Red Hat's immutable tags to ensure reproducible builds. This will also teach Renovate to only apply z-stream updates for ubi8/go-toolset, and y-stream updates for ubi8/ubi-minimal.

[openshift-ci-robot]

@adambkaplan: This pull request explicitly references no jira issue.

In response to this:

Use Red Hat's immutable tags to ensure reproducible builds. This will also teach Renovate to only apply z-stream updates for ubi8/go-toolset, and y-stream updates for ubi8/ubi-minimal.

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 openshift-eng/jira-lifecycle-plugin repository.

[openshift-ci]

@adambkaplan: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
ci/prow/security	a1e6796	link	false	/test security

Full PR test history. Your PR dashboard.

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[sayan-biswas]

/approved
/lgtm

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: adambkaplan, sayan-biswas

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