fix: backport maintenance-mode changes for successful failover

What does this MR do?

This is a backport of !1762 (merged) to GET 3.5.x

It allows for clean vendoring down of the fix. This fix allows for maintenance mode to be retried on a fresh toolbox pod if it is rotated before / during the execution of this task. Without this the failover playbook needs to be executed twice for a successful failover.

Related issues

#1192 (closed)

Author's checklist

When ready for review, the Author applies the workflowready for review label and mention @gitlab-org/software-delivery/get-maintainers:

• Merge request:
  • Corresponding Issue raised and reviewed by the GET maintainers team.
  • Merge Request Title and Description are up-to-date, accurate, and descriptive
  • MR targeting the appropriate branch
  • MR has a green pipeline
  • MR has no new security alerts in the widget from the Secret Detection and IaC Scan (SAST) jobs.
• Code:
  • Check the area changed works as expected across all expected permutations.
  • Check that the changes work across upgrades.
  • Documentation created/updated in the same MR if applicable