Fix position of done call in Log level test

[fearful-symmetry]

What does this PR do?

This changes the position of a waitgroup Done() call to fix a potential panic, as we can occasionally hit the gotStopped call more than once. The rest of the tests already do this, I just forgot to adjust this test.

Why is it important?

This can cause occasional test failures.

[mergify]

This pull request does not have a backport label.
If this is a bug or security fix, could you label this PR @fearful-symmetry? 🙏.
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

[elasticmachine]

💔 Build Failed

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• Start Time: 2023-02-27T19:02:31.514+0000

• Duration: 12 min 48 sec

Steps errors

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Go unitTest

• Took 0 min 29 sec . View more details here
• Description: mage unitTest

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