• This change is a better way of setting up multi-fs tests.
• Avoids the unnecessary setup, when writing a multi-fs test. Avoids creating the default filesystem, deleting it and creating the required filesystems, mounting them. Instead, it uses the filesystems created using REQUIRE_BACKUP_FILESYSTEM for conducting tests.
• This change consequently fixes the old/deleted filesystems appearing in the perf stats output and thus making it stale output. This is the reason the trackers (below) are attached. It was not the right way to setup a multi-fs test and there are no issues with the mgr o/p.
• Drops unused function parameters.

Fixes: https://tracker.ceph.com/issues/68001
Fixes: https://tracker.ceph.com/issues/68446

Contribution Guidelines

• To sign and title your commits, please refer to Submitting Patches to Ceph.

• If you are submitting a fix for a stable branch (e.g. "quincy"), please refer to Submitting Patches to Ceph - Backports for the proper workflow.

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Checklist

• Tracker (select at least one)
  • References tracker ticket
  • Very recent bug; references commit where it was introduced
  • New feature (ticket optional)
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• Component impact
  • Affects Dashboard, opened tracker ticket
  • Affects Orchestrator, opened tracker ticket
  • No impact that needs to be tracked
• Documentation (select at least one)
  • Updates relevant documentation
  • No doc update is appropriate
• Tests (select at least one)
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