[master](backport #29297) Agent configuration overridden by default fleet config

[mergify]

This is an automatic backport of pull request #29297 done by Mergify.
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On branch mergify/bp/master/pr-29297
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nothing to commit, working tree clean

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[elasticmachine]

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• Start Time: 2021-12-09T16:10:09.443+0000

• Duration: 19 min 50 sec

• Commit: 1b9658b

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Skipped	0
Total	3

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[andrewkroh]

This is an empty "backport" (master PR to master branch).