test: reduce flakiness in test-heapdump-http2

[joyeecheung]

By the time the response event is emitted on the client's side, the file may have already been fully piped and the stream pipe may have been destroyed, so the test should not look for the stream pipe in the snapshot.

This doesn't seem to reproduce in the CI (the CI is seeing a timeout caused by the deadlock instead) but locally when I was trying to reproduce the deadlock with with tools/test.py -J --repeat=1000 pummel/test-heapdump-http2 using a shared library build on macOS, this failure comes up first instead of the deadlock because the uv_try_write done for writing the file finishes too fast & synchronously - maybe because it's already cached under repeated runs - destroying the stream pipe already before the snapshot is taken.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 90.17%. Comparing base (723d7bb) to head (7f080a3). Report is 23 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #58148      +/-   ##
==========================================
- Coverage   90.17%   90.17%   -0.01%     
==========================================
  Files         630      630              
  Lines      186473   186473              
  Branches    36613    36610       -3     
==========================================
- Hits       168160   168157       -3     
+ Misses      11128    11118      -10     
- Partials     7185     7198      +13     

see 36 files with indirect coverage changes

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[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/66585/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/66599/

[nodejs-github-bot]

Landed in 5f48fddd3a61502efc40bb218211ed71e17792e5