aio: task_abort was a mistake

[gdamore]

The use of task_abort to prematurely fail an aio at scheduling time was a mistake, because it could have led to duplicate calls to nng_aio_finish(). We do need to ensure that we leave an indicator so that nni_aio_schedule can return the abort status to caller, in the case that abort is called between the nni_aio_begin and nni_aio_schedule calls.

fixes #

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[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 3 lines in your changes missing coverage. Please review.

Project coverage is 81.80%. Comparing base (8af6bef) to head (3ca7bcc).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/core/aio.c	66.66%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1978      +/-   ##
==========================================
- Coverage   81.92%   81.80%   -0.12%     
==========================================
  Files          95       95              
  Lines       24071    24063       -8     
  Branches     3207     3207              
==========================================
- Hits        19719    19685      -34     
- Misses       4279     4306      +27     
+ Partials       73       72       -1     

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