Don't call shutdown() after an exception (backport #1400)

[mergify]

Closes #1383 acc. to the hint given by @firesurfer

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This is an automatic backport of pull request #1400 done by Mergify.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 66.31%. Comparing base (7904d4b) to head (8d5f1e7).
Report is 1 commits behind head on humble.

Additional details and impacted files

@@            Coverage Diff             @@
##           humble    #1411      +/-   ##
==========================================
+ Coverage   66.27%   66.31%   +0.03%     
==========================================
  Files         110      110              
  Lines       12662    12656       -6     
  Branches     7813     7813              
==========================================
+ Hits         8392     8393       +1     
- Misses       1409     1411       +2     
+ Partials     2861     2852       -9     

Flag	Coverage Δ
unittests	66.31% <100.00%> (+0.03%)	⬆️

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

Files with missing lines	Coverage Δ
...est_nodes/publisher_forward_position_controller.py	86.04% <100.00%> (+5.61%)	⬆️
...est_nodes/publisher_joint_trajectory_controller.py	55.37% <100.00%> (+1.33%)	⬆️

... and 3 files with indirect coverage changes