Added test for SubPathExpr

[enrichman]

#441 fixed an issue about a CreateContainerConfigError coming from an invalid VolumeMount.
Creating a Pod that is erroring and then trying to fix it updating the annotation was not working.

This PR just adds a test to avoid regressions, while trying to fix #495.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 59.31%. Comparing base (8856419) to head (658a568).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #569      +/-   ##
==========================================
- Coverage   59.61%   59.31%   -0.31%     
==========================================
  Files          56       56              
  Lines        5255     5255              
==========================================
- Hits         3133     3117      -16     
- Misses       1837     1845       +8     
- Partials      285      293       +8     

Flag	Coverage Δ
cli	53.35% <ø> (-0.08%)	⬇️
controller	56.78% <ø> (-0.36%)	⬇️
e2e	56.78% <ø> (-0.36%)	⬇️
unit	36.32% <ø> (-0.04%)	⬇️

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