Fix denial of service caused by a 404 from elasticsearch to managed logstashes

[zwsyscall]

This PR fixes a bug caused by #17052 where a single 404 return from elasticsearch can lead to a prolonged denial of service in Logstash as its pipelines are removed.
Returns @cached_pipelines.

• Closes Unexpected pipeline shutdown with central-managed configurations #17980
• Relates CPM handle 404 response gracefully with user-friendly log #17052

[cla-checker-service]

💚 CLA has been signed

[github-actions]

🤖 GitHub comments

Expand to view the GitHub comments

Just comment with:

• run docs-build : Re-trigger the docs validation. (use unformatted text in the comment!)

[mergify]

This pull request does not have a backport label. Could you fix it @zwsyscall? 🙏
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.
• If no backport is necessary, please add the backport-skip label

[zwsyscall]

This should be backported to 8.17, 8.18, 8.19, and 9.0, I can't add the tags myself.