[24110] Fix wrong update of default locators (backport #6273)

[mergify]

Description

This PR fixes a bug in which the defaultLocatorList was being wrongly updated after calling set_qos. This corner-case occurred only when the metatraffic locators are set, but the default ones are left empty (not configured) and Fast DDS automatically configures them. If in this situation the participant needs to perform mutation tries in one of their ports, the participant will not preserve the mutation tries value, and in later updates will wrongly update the locator.

Additionally I have refactor the communication tests to properly apply argument sleep_before_exec, which was being applied to the main thread rather than to the specific process.
Note that in the new test the seed is being specifically set, which translates into domain 31 (randomly selected). This is required to manually set the proper ports in the XML file configuration, which are mapped to the domain 31.

@Mergifyio backport 3.4.x 3.2.x 2.14.x

Contributor Checklist

• Commit messages follow the project guidelines.

• The code follows the style guidelines of this project.

• 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.
• N/A: 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 #6273 done by [Mergify](https://mergify.com).