Don't delete existing file if download fails

[JWaters02]

What It Does

Fixes #2595

How to Test

Run command to download a hekin chonker of a file (that takes a while to download) (successfully). Now run the command again but this time kill your network halfway through the download. See that the original file is no longer deleted.

Review Checklist
I certify that I have:

• updated the changelog
• manually tested my changes
• added/updated automated unit/integration tests
• created/ran system tests (provide build number if applicable)
• followed the contribution guidelines

Additional Comments

[codecov]

Codecov Report

❌ Patch coverage is 85.71429% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.81%. Comparing base (fdd6221) to head (d42834b).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
packages/zosfiles/src/methods/download/Download.ts	85.71%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2618      +/-   ##
==========================================
- Coverage   91.81%   91.81%   -0.01%     
==========================================
  Files         644      644              
  Lines       19143    19154      +11     
  Branches     4124     4241     +117     
==========================================
+ Hits        17577    17586       +9     
- Misses       1564     1566       +2     
  Partials        2        2              

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[JWaters02]

I don't understand what is wrong with this PR in the code analysis, the link opens in my PR but then opens issues that are really old

[sonarqubecloud]

Quality Gate passed

Issues
2 New issues
0 Accepted issues

Measures
0 Security Hotspots
94.3% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[traeok]

Changes LGTM, thanks Joshua