fix: logcli: Check for errors before checking for exists when fetching data (backport k227)

[loki-gh-app]

Backport 9e7d2f2 from #14780

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What this PR does / why we need it:
When getting data from object storage, we're first checking for the exists return and only then for the error returned. Everytime an error is returned an exists=false is also returned, and that is taken more precedence than the error itself.

Which issue(s) this PR fixes:
Fixes #

Special notes for your reviewer:

Checklist

• Reviewed the CONTRIBUTING.md guide (required)
• Documentation added
• Tests updated
• Title matches the required conventional commits format, see here
  • Note that Promtail is considered to be feature complete, and future development for logs collection will be in Grafana Alloy. As such, feat PRs are unlikely to be accepted unless a case can be made for the feature actually being a bug fix to existing behavior.
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