Speed up base image unit test with local registry

[halvards]

Also follow my own advice to defer Close() 😇

[codecov-commenter]

Codecov Report

Merging #429 (a83e016) into main (ae594dc) will decrease coverage by 0.21%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #429      +/-   ##
==========================================
- Coverage   53.50%   53.28%   -0.22%     
==========================================
  Files          36       36              
  Lines        1828     1828              
==========================================
- Hits          978      974       -4     
- Misses        699      703       +4     
  Partials      151      151              

Impacted Files	Coverage Δ
pkg/commands/config.go	55.96% <0.00%> (-3.67%)	⬇️

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