Catch unsupported Systemd Watchdog

[mpass99]

Closes #644

[codecov]

Codecov Report

Attention: Patch coverage is 20.00000% with 4 lines in your changes missing coverage. Please review.

Project coverage is 76.10%. Comparing base (c5718b5) to head (08a8a29).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
cmd/poseidon/main.go	20.00%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #689      +/-   ##
==========================================
- Coverage   76.19%   76.10%   -0.10%     
==========================================
  Files          43       43              
  Lines        3642     3645       +3     
==========================================
- Hits         2775     2774       -1     
- Misses        633      635       +2     
- Partials      234      236       +2     

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[MrSerth]

Works like a charm, thank you! 🌈