Fix Container Scanning for Kubernetes Runners

What does this MR do?

Fix Container Scanning job when using Kubernetes Runners.

What are the relevant issue numbers?

closes https://gitlab.com/gitlab-org/gitlab-ee/issues/6636 and https://gitlab.com/gitlab-org/gitlab-ee/issues/5763

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• [-] Documentation created/updated via this MR
• [-] Documentation reviewed by technical writer or follow-up review issue created
• Tests added for this feature/bug
• [-] Tested in all supported browsers
• Conforms to the code review guidelines
• [-] Conforms to the merge request performance guidelines
• [-] Conforms to the style guides
• [-] Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• Security reports checked/validated by reviewer