tests(dns): flakiness due to hook conflict

[StarlightIbuki]

Summary

The test suits hook the query function and uses a shared variable to change the hook. This causes conflicts when test A has an aysnc query still running, and B swaps the hook function, so the function will be called more than expected times.

Checklist

• [N/A] The Pull Request has tests
• [x] A changelog file has been added to CHANGELOG/unreleased/kong or adding skip-changelog label on PR if unnecessary. README.md
• [x] The Pull Request has backports to all the versions it needs to cover
• [N/A] There is a user-facing docs PR against https://github.com/Kong/docs.konghq.com - PUT DOCS PR HERE

Issue reference

Fix KAG-4519

[team-gateway-bot]

Successfully created cherry-pick PR for master:

• https://github.com/kong/kong-ee/pull/9614