Fix systemctl stop time delay

[knoepfel]

This PR solves #626 and it is a first step toward fixing issue #639.The reason for the blocking is that all channels were brought online before the server's serve_forever() call was made. This PR calls serve_forever() much earlier and starts the channels using a separate thread. This solves one issue but it the de-client --status call still hangs even after serve_forever() has been called.

[codecov]

Codecov Report

Merging #648 (8cc99be) into master (f4dc7da) will decrease coverage by 0.08%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #648      +/-   ##
==========================================
- Coverage   97.45%   97.36%   -0.09%     
==========================================
  Files          49       49              
  Lines        2943     2960      +17     
  Branches      470      471       +1     
==========================================
+ Hits         2868     2882      +14     
- Misses         50       53       +3     
  Partials       25       25              

Flag	Coverage Δ
python-3.10	97.19% <100.00%> (-0.06%)	⬇️
python-3.6	96.91% <100.00%> (-0.06%)	⬇️

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Impacted Files	Coverage Δ
.../decisionengine/framework/engine/DecisionEngine.py	93.11% <100.00%> (-0.34%)	⬇️
...c/decisionengine/framework/engine/SourceWorkers.py	98.51% <100.00%> (+0.01%)	⬆️

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[lgtm-com]

This pull request introduces 1 alert when merging 5307958 into f4dc7da - view on LGTM.com

new alerts:

• 1 for Module is imported with 'import' and 'import from'