fix: ensure testnetApp cleanup on error in testnetify

[MrEeeeet111]

Description

Reopen #25655

[codecov]

Codecov Report

❌ Patch coverage is 0% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 70.42%. Comparing base (7e9ad4f) to head (cacda23).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
server/start.go	0.00%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #25660      +/-   ##
==========================================
- Coverage   70.42%   70.42%   -0.01%     
==========================================
  Files         830      830              
  Lines       54052    54058       +6     
==========================================
+ Hits        38068    38072       +4     
- Misses      15984    15986       +2     

Files with missing lines	Coverage Δ
server/start.go	18.88% <0.00%> (-0.22%)	⬇️

... and 1 file with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.