filebeat: Fix flaky test case on macOS

[VihasMakwana]

Proposed commit message

This PR fixes following test cases which are flaky for macOS:

• tests/system/test_harvester.py::Test::test_debug_reader
• tests/system/test_crawler.py::Test::test_tail_files
• tests/system/test_crawler.py::Test::test_encodings
• tests/system/test_registrar.py::Test::test_restart_state_reset_ttl_no_clean_inactive
• tests/system/test_registrar.py::Test::test_restart_state_reset
• tests/system/test_registrar.py::Test::test_restart_state
• tests/system/test_registrar.py::Test::test_registry_file_update_permissions
• tests/system/test_shutdown.py::Test::test_shutdown

On MacOS, the FQDN lookup takes some time (~5 seconds) before signal handlers are set up

• the lingering FQDN lookup code is here
  To make sure that the tests are passed, we need to increase the timeout by few seconds in each of the failing cases.

You can view the full discussion https://elastic.slack.com/archives/C047NDNGUMU/p1717091056290869.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

Fixes #39613

[elasticmachine]

Pinging @elastic/elastic-agent-data-plane (Team:Elastic-Agent-Data-Plane)

[mergify]

This pull request does not have a backport label.
If this is a bug or security fix, could you label this PR @VihasMakwana? 🙏.
For such, you'll need to label your PR with:

• The upcoming major version of the Elastic Stack
• The upcoming minor version of the Elastic Stack (if you're not pushing a breaking change)

To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-v8./d.0 is the label to automatically backport to the 8./d branch. /d is the digit

[belimawr]

A general question: Do we need those tests using the FQDN? Could we just disable it as those tests are not testing the FQDN and have the suit run faster?

[VihasMakwana]

A general question: Do we need those tests using the FQDN? Could we just disable it as those tests are not testing the FQDN and have the suit run faster?

Hmm, I'm not sure if we can selectively disable FQDN. These integration test cases try to run the filebeat binary and test for output.
Also, this problem is specific to Darwin based systems.
On other systems, the wait calls should resolve quickly.

[belimawr]

A general question: Do we need those tests using the FQDN? Could we just disable it as those tests are not testing the FQDN and have the suit run faster?

Hmm, I'm not sure if we can selectively disable FQDN. These integration test cases try to run the filebeat binary and test for output. Also, this problem is specific to Darwin based systems. On other systems, the wait calls should resolve quickly.

The Elastic-Agent has got a flag to select if we're using FQDN or not, I don't fully recall how that works for a standalone Beat, it might be possible.

But if the OS is slow to respond regardless of how we query it, then there is not much we can do.

Anyway, the PR looks good now!