Fix realtime publisher race condition upon initialization (backport #309)

[mergify]

Should fix : #24
Closes: #308

@bijoua29 can you test this and see if this helps?

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This is an automatic backport of pull request #309 done by Mergify.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 83.33333% with 1 line in your changes missing coverage. Please review.

Project coverage is 85.87%. Comparing base (f5f79db) to head (84a9b93).

Files with missing lines	Patch %	Lines
...ools/include/realtime_tools/realtime_publisher.hpp	83.33%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##            jazzy     #311      +/-   ##
==========================================
- Coverage   86.34%   85.87%   -0.47%     
==========================================
  Files          19       19              
  Lines        1318     1317       -1     
  Branches      115      113       -2     
==========================================
- Hits         1138     1131       -7     
- Misses        105      111       +6     
  Partials       75       75              

Flag	Coverage Δ
unittests	85.87% <83.33%> (-0.47%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...ools/include/realtime_tools/realtime_publisher.hpp	90.90% <83.33%> (-6.77%)	⬇️

... and 2 files with indirect coverage changes

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