Enable the "diego_cnb" flag for "luna"

[jochenehret]

WHAT is this change about?

Enable the Cloud Native Buildpack flag on the fresh/luna environment. The CNB CATs suite is already enabled.

What customer problem is being addressed? Use customer persona to define the problem e.g. Alana is unable to...

Alana wants to have the CNB feature validated in the cf-deployment pipeline.

Please provide any contextual information.

cloudfoundry/community#591

Has a cf-deployment including this change passed cf-acceptance-tests?

• YES (pipeline has already been uploaded to Concourse)
• NO

Does this PR introduce a breaking change? Please take a moment to read through the examples before answering the question.

• YES - please choose the category from below. Feel free to provide additional details.
• NO

How should this change be described in cf-deployment release notes?

Feature is already released, this is just a configuration / feature flag update for the test environment.

Does this PR introduce a new BOSH release into the base cf-deployment.yml manifest or any ops-files?

• YES - please specify
• NO

Does this PR make a change to an experimental or GA'd feature/component?

• experimental feature/component
• GA'd feature/component

Please provide Acceptance Criteria for this change?

The "fresh-cats" job must be green.

What is the level of urgency for publishing this change?

• Urgent - unblocks current or future work
• Slightly Less than Urgent