[hipDNN] Fix unstable user log test.

[CMiservaAMD]

Motivation

Test was susceptible to race conditions.

Technical Details

Replaced sleep() with signals between threads to ensure threads were run to generate the needed data for the test.

Test Plan

Test Result

Submission Checklist

• Look over the contributing guidelines at https://github.com/ROCm/ROCm/blob/develop/CONTRIBUTING.md#pull-requests.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.

❌ Your project status has failed because the head coverage (47.50%) is below the target coverage (80.00%). You can increase the head coverage or adjust the target coverage.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #6471      +/-   ##
===========================================
+ Coverage    66.59%   66.60%   +0.01%     
===========================================
  Files         2176     2177       +1     
  Lines       321082   321475     +393     
  Branches     41481    41539      +58     
===========================================
+ Hits        213810   214101     +291     
- Misses       92635    92712      +77     
- Partials     14637    14662      +25     

Flag	Coverage Δ		*Carryforward flag
hipBLAS	90.67% <ø> (ø)		Carriedforward from 72d355b
hipBLASLt	39.95% <ø> (ø)		Carriedforward from 72d355b
hipCUB	82.21% <ø> (ø)		Carriedforward from 72d355b
hipDNN	82.41% <100.00%> (-0.07%)	⬇️
hipFFT	55.00% <ø> (ø)		Carriedforward from 72d355b
hipRAND	76.12% <ø> (ø)		Carriedforward from 72d355b
rocBLAS	48.11% <ø> (ø)		Carriedforward from 72d355b
rocFFT	47.50% <ø> (ø)		Carriedforward from 72d355b
rocPRIM	38.96% <ø> (ø)		Carriedforward from 72d355b
rocRAND	57.09% <ø> (ø)		Carriedforward from 72d355b
rocSPARSE	71.52% <ø> (ø)		Carriedforward from 72d355b
rocThrust	91.37% <ø> (ø)		Carriedforward from 72d355b

*This pull request uses carry forward flags. Click here to find out more.

Files with missing lines	Coverage Δ
.../include/hipdnn_test_sdk/utilities/LogRecorder.hpp	99.14% <100.00%> (+0.04%)	⬆️

... and 3 files with indirect coverage changes

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[SamuelReeder]

Generally LGTM! Potentially minor comments, but I think they're worth addressing.