Avoid minio connection if cache is sufficient

[ponyisi]

Address #295 by only verifying that we only list the S3 buckets when we have a cached record if we are trying to get local files when only signed URLs are cached, or vice versa. Fix a number of tests.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.71%. Comparing base (daed1b1) to head (91e4573).
Report is 3 commits behind head on 3.0_develop.

Additional details and impacted files

@@               Coverage Diff               @@
##           3.0_develop     #439      +/-   ##
===============================================
+ Coverage        81.73%   82.71%   +0.98%     
===============================================
  Files               26       26              
  Lines             1341     1423      +82     
===============================================
+ Hits              1096     1177      +81     
- Misses             245      246       +1     

Flag	Coverage Δ
unittests	82.71% <ø> (+0.98%)	⬆️

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[BenGalewsky]

yay, glad this works!