Fix bad caching to prevent already devirtualized files getting lost

[stxue1]

Closes #4959

We were caching already devirtualized files in the virtualized-to-devirtualized cache, which caused conflicts when the task/job cleaned up its files but the workflow attempts to access it again from the "virtualized" url.

This separates the caching a bit so it only adds it to the cache when we actually have a virtualized file to devirtualize. This also lets the devirtualization step start using the cache, which it wasn't doing before.

Changelog Entry

To be copied to the draft changelog by merger:

• Fixed a bug where already devirtualized files get lost

Reviewer Checklist

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  • [ ] Read through the code changes. Make sure that it doesn't have:
  • [ ] Addition of trailing whitespace.
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Merger Checklist

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