fix(add_kubernetes_metadata): wait for init to complete during close

[kruskall]

Proposed commit message

prevent goroutine leak and wait for init to complete when closing the processor

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. Where relevant, I have used the stresstest.sh script to run them under stress conditions and race detector to verify their stability.
• I have added an entry in ./changelog/fragments using the changelog tool.

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Related issues

• Related to [Flaky test] TestGenerateProcessorList: panic: Log in goroutine after TestGenerateProcessorList has completed #47528

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[mergify]

This pull request does not have a backport label.
If this is a bug or security fix, could you label this PR @kruskall? 🙏.
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-8./d is the label to automatically backport to the 8./d branch. /d is the digit
• backport-active-all is the label that automatically backports to all active branches.
• backport-active-8 is the label that automatically backports to all active minor branches for the 8 major.
• backport-active-9 is the label that automatically backports to all active minor branches for the 9 major.

[elasticmachine]

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

[AndersonQ]

Just to double-check, you're trying to avoid the situation where Close is called while init is still executing.
So, in that case, shouldn't this call be the 1st thing, to ensure:

• close only runs after init has finished
• close closes all resources init created?

Also, as it not so straight forward to get why it's calling Do with an empty function, I believe it would be good to add a comment here.

[kruskall]

Thanks! 🙇

The goal here is to avoid there are goroutines leaking after close has been called (which can happen if init hasn't finished).
Those are good points, added a comment and updated the code 👍