[22995] Fix MacOS nightly flaky tests (backport #5738)

[mergify]

Description

This PR provides some fixes in a couple of tests failing in the nighties

@Mergifyio backport 3.1.x 2.14.x 2.10.x

Contributor Checklist

• Commit messages follow the project guidelines.

• The code follows the style guidelines of this project.

• N/A Tests that thoroughly check the new feature have been added/Regression tests checking the bug and its fix have been added; the added tests pass locally

• N/A Any new/modified methods have been properly documented using Doxygen.

• N/A Any new configuration API has an equivalent XML API (with the corresponding XSD extension)

• Changes are backport compatible: they do NOT break ABI nor change library core behavior.

• Changes are API compatible.

• N/A New feature has been added to the versions.md file (if applicable).

• N/A New feature has been documented/Current behavior is correctly described in the documentation.

• Applicable backports have been included in the description.

Reviewer Checklist

• The PR has a milestone assigned.
• The title and description correctly express the PR's purpose.
• Check contributor checklist is correct.
• If this is a critical bug fix, backports to the critical-only supported branches have been requested.
• Check CI results: changes do not issue any warning.
• Check CI results: failing tests are unrelated with the changes.

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This is an automatic backport of pull request #5738 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 6d0d853 has failed:

On branch mergify/bp/3.1.x/pr-5738
Your branch is up to date with 'origin/3.1.x'.

You are currently cherry-picking commit 6d0d853c.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   test/blackbox/common/BlackboxTestsDiscovery.cpp
	both modified:   test/blackbox/common/DDSBlackboxTestsMonitorService.cpp

no changes added to commit (use "git add" and/or "git commit -a")

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[Mario-DL]

Flaky tests affects to tests checking non-existing features in 3.1.x (ExtendedIncompatibleQoS for monitor service and Builtin Flow Controllers), closing this backport