[7.17](backport #1854) Add error detail to catch-all HTTP response

[mergify]

This is an automatic backport of pull request #1854 done by Mergify.
Cherry-pick of c51c26f has failed:

On branch mergify/bp/7.17/pr-1854
Your branch is up to date with 'origin/7.17'.

You are currently cherry-picking commit c51c26f.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   cmd/fleet/error.go

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   CHANGELOG.next.asciidoc

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/github/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

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[elasticmachine]

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• Start Time: 2022-09-20T11:14:02.780+0000

• Duration: 9 min 1 sec

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Test	Results
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Passed	236
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Total	236

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