return correct errors in rare failure situations

[bobcallaway]

while analyzing the codebase, I noticed in three situations that we would return an incorrect err which would make debugging more challenging. this returns the correct err in each situation.

[codecov]

Codecov Report

❌ Patch coverage is 20.00000% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 26.17%. Comparing base (488eb97) to head (7caa1f4).
⚠️ Report is 636 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/trillianclient/trillian_client.go	0.00%	4 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #2753       +/-   ##
===========================================
- Coverage   66.46%   26.17%   -40.29%     
===========================================
  Files          92      191       +99     
  Lines        9258    20127    +10869     
===========================================
- Hits         6153     5269      -884     
- Misses       2359    14030    +11671     
- Partials      746      828       +82     

Flag	Coverage Δ
e2etests	49.50% <0.00%> (+1.94%)	⬆️
unittests	16.72% <20.00%> (-30.97%)	⬇️

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