[8.4](backport #1896) Catch error in waitBulkAction. Add bulk.WithRetryOnConflict(3) in multiple places.

[mergify]

This is an automatic backport of pull request #1896 done by Mergify.
Cherry-pick of f77b97c has failed:

On branch mergify/bp/8.4/pr-1896
Your branch is up to date with 'origin/8.4'.

You are currently cherry-picking commit f77b97c.
  (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:   internal/pkg/api/handleAck.go
	modified:   internal/pkg/bulk/opBulk.go
	modified:   internal/pkg/coordinator/monitor.go
	modified:   internal/pkg/dl/servers.go

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   CHANGELOG.next.asciidoc
	both modified:   internal/pkg/policy/policy_output.go

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: 2022-09-30T17:58:38.804+0000

• Duration: 11 min 6 sec

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Test	Results
Failed	0
Passed	307
Skipped	1
Total	308

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[blakerouse]

+1