Export missing defaults when set False

[pdxlocations]

Some older protobufs default to True. When users set them to False, they are excluded from --export-config. When using --configure, these keys are not set to False.

This PR sets these keys to False in --export-config if they are missing.

[codecov]

Codecov Report

❌ Patch coverage is 90.90909% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 60.13%. Comparing base (172c123) to head (0261313).

Files with missing lines	Patch %	Lines
meshtastic/__main__.py	90.90%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #807      +/-   ##
==========================================
+ Coverage   60.05%   60.13%   +0.08%     
==========================================
  Files          24       24              
  Lines        4208     4219      +11     
==========================================
+ Hits         2527     2537      +10     
- Misses       1681     1682       +1     

Flag	Coverage Δ
unittests	60.13% <90.90%> (+0.08%)	⬆️

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