release-24.3: backup: improve datadriven test cleanup

[jeffswenson]

Backport 1/1 commits from #154687.

/cc @cockroachdb/release

Release justification: test only change.

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Previously, the datadriven test harness would tear down clusters in order. This makes it difficult to troubleshoot stuck tear downs because there are goroutines for a running server mixed in with goroutines for a server with a stuck shutdown.

Release note: none
Informs: #145079

[blathers-crl]

Thanks for opening a backport.

Before merging, please confirm that it falls into one of the following categories (select one):

• Non-production code changes. Includes test-only changes, build system changes, etc.
• Fixes for serious issues. Defined in the policy as correctness, stability, or security issues, data corruption/loss, significant performance regressions, breaking working and widely used functionality, or an inability to detect and debug production issues.
• Other approved changes. These changes must be gated behind a disabled-by-default feature flag unless there is a strong justification not to.

Add a brief release justification to the PR description explaining your selection.

Also, confirm that the change does not break backward compatibility and complies with all aspects of the backport policy.

All backports must be reviewed by the TL and EM for the owning area.

[blathers-crl]

✅ PR #155116 is compliant with backport policy

Confidence: high
Backward compatible: true
Explanation: The PR is modifying a test file with a *_test.go suffix, specifically datadriven_test.go within the pkg/ccl/backupccl directory. According to the backport policy, changes that only affect non-production code, tests, or development tools are exempt from the standard backport policy requirements. Therefore, this PR, which is described as a 'test only change' in the PR body, aligns with the exception for Non-Production and Test-Only Changes. It adds clarity to the test execution process without affecting production functionality.

_{🦉 Hoot! I am a Blathers, a bot for CockroachDB. My owner is dev-inf.}

[cockroach-teamcity]

This change is