Bugfix: By default, MAC commands answers should only be sent once

[nondetalle]

Current default device behavior (i.e., resend MAC command answers until a downlink is received from the network) is wrong. According to LoRaWAN 1.0.4 specifications, this only applies to RXParamSetupAns, RXTimingSetupAns, TXParamSetupAns, and DlChannelAns, while all other uplink MAC commands are meant to be sent only once.

[codecov]

Codecov Report

❌ Patch coverage is 59.09091% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.52%. Comparing base (67bcaef) to head (a159b5c).

Files with missing lines	Patch %	Lines
model/lora-frame-header.cc	47.05%	9 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #224   +/-   ##
========================================
  Coverage    86.51%   86.52%           
========================================
  Files           68       68           
  Lines         7876     7880    +4     
========================================
+ Hits          6814     6818    +4     
  Misses        1062     1062           

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