fix: duplicate stacktrace on engine error

[wallashss]

Description

This is a follow up on this change vllm-project/vllm#9023 of vllm upstream

How Has This Been Tested?

See vllm-project/vllm#9023

Merge criteria:

• The commits are squashed in a cohesive manner and have meaningful messages.
• Testing instructions have been added in the PR body (for PRs involving changes that are not immediately obvious).
• The developer has manually tested the changes and verified that the changes work

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 95.65217% with 1 line in your changes missing coverage. Please review.

Project coverage is 62.46%. Comparing base (d66fff7) to head (199962e).

Files with missing lines	Patch %	Lines
tests/test_grpc_server.py	94.73%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #171      +/-   ##
==========================================
+ Coverage   61.54%   62.46%   +0.92%     
==========================================
  Files          28       28              
  Lines        1698     1721      +23     
  Branches      210      211       +1     
==========================================
+ Hits         1045     1075      +30     
+ Misses        556      544      -12     
- Partials       97      102       +5     

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