Fixing flaky tests

[norro]

• Fix flaky launch tests
• Fix that processes sometimes don't react to SIGINT properly, leaving ugly error messages in the test procedure (not failing the testsm though)

https://github.com/micro-ROS/system_modes/issues/70

[codecov[bot]]

Codecov Report

Merging #71 (b7a24d9) into master (eeabfcb) will increase coverage by 6.67%. The diff coverage is n/a.

@@            Coverage Diff             @@
##           master      #71      +/-   ##
==========================================
+ Coverage   21.08%   27.76%   +6.67%     
==========================================
  Files          14       14              
  Lines        1048     1048              
  Branches      754      754              
==========================================
+ Hits          221      291      +70     
+ Misses        524      280     -244     
- Partials      303      477     +174     

Impacted Files	Coverage Δ
system_modes/src/system_modes/mode_impl.cpp	38.37% <0.00%> (+2.32%)	:arrow_up:
system_modes/src/system_modes/mode_inference.cpp	35.69% <0.00%> (+5.44%)	:arrow_up:
system_modes/src/system_modes/mode_observer.cpp	20.00% <0.00%> (+6.00%)	:arrow_up:
system_modes/src/system_modes/mode_manager.cpp	16.54% <0.00%> (+16.16%)	:arrow_up:
system_modes/include/system_modes/mode_manager.hpp	100.00% <0.00%> (+100.00%)	:arrow_up:
...ystem_modes/include/system_modes/mode_handling.hpp	100.00% <0.00%> (+100.00%)	:arrow_up:

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