Update AKS acceptance/mock tests to use kubernetes 1.27.9

[gshaw-pivotal]

1. What this PR does / why we need it:

AKS acceptance tests started failing as the kubernetes version they use (1.26.6) is no longer available in the Azure region the test executes against. Updated to kubernetes version 1.27.9

2. Which issue(s) this PR fixes

N/A

3. Additional information

• Kubernetes 1.26.x in Azure is reaching EOL and various patch versions are starting to become unavailable for use.
• Kubernetes 1.27 has EOL in Jul 2024 and LTS until Jul 2025.
• To make it easier to update the version in the future, added a variable to hold the version string. Future updates only therefore need to change the value of this variable

4. Special notes for your reviewer

Tested locally in both mock and acceptance mode (against real stack).

[vmwclabot]

@gshaw-pivotal, you must sign every commit in this pull request acknowledging our Developer Certificate of Origin before your changes are merged. This can be done by adding Signed-off-by: John Doe <john.doe@email.org> to the last line of each Git commit message. The e-mail address used to sign must match the e-mail address of the Git author. Click here to view the Developer Certificate of Origin agreement.

• Commit c06ec5bd4a74479090dcb929fda8077f4daa60c6 must be signed by gshaw+github@pivotal.io

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 25.31%. Comparing base (7b21fe2) to head (663f12f).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #382 +/- ## ======================================= Coverage 25.31% 25.31% ======================================= Files 195 195 Lines 16845 16845 ======================================= Hits 4264 4264 Misses 12363 12363 Partials 218 218 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.