add flux module path

[andre-merzky]

This fixes radical-cybertools/radical.pilot/issues/3149

[codecov]

Codecov Report

Attention: Patch coverage is 10.52632% with 17 lines in your changes missing coverage. Please review.

Project coverage is 62.22%. Comparing base (397654d) to head (dc4f38f).
Report is 197 commits behind head on devel.

Files with missing lines	Patch %	Lines
src/radical/utils/flux.py	6.66%	14 Missing ⚠️
src/radical/utils/debug.py	25.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##            devel     #400      +/-   ##
==========================================
- Coverage   62.37%   62.22%   -0.15%     
==========================================
  Files          61       61              
  Lines        6758     6775      +17     
==========================================
+ Hits         4215     4216       +1     
- Misses       2543     2559      +16     

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[mtitov]

LGTM!

p.s. tested it without setting PYTHONPATH on my side, python flux was discovered correctly