Correct use of attack/defense power

[simon33-2]

Resolves test3 referred to in #1270

This code base uses a boolean parameter for to pick between attack and defence. Sometimes true = attack, sometimes true = defense! WTF! Anyway, this resolves a few instances of this problem in the removal of must die units code.

[codecov-io]

Codecov Report

Merging #2366 into master will not change coverage.
The diff coverage is 100%.

@@            Coverage Diff            @@
##             master    #2366   +/-   ##
=========================================
  Coverage     20.12%   20.12%           
  Complexity     5718     5718           
=========================================
  Files           822      822           
  Lines         73744    73744           
  Branches      12424    12426    +2     
=========================================
  Hits          14844    14844           
+ Misses        56845    56843    -2     
- Partials       2055     2057    +2

Impacted Files	Coverage Δ	Complexity Δ
...mes/strategy/triplea/delegate/MustFightBattle.java	62.55% <100%> (ø)	341 <0> (+2)	⬆️
...rategy/triplea/attachments/UnitTypeComparator.java	35.71% <0%> (-7.15%)	10% <0%> (-1%)
src/main/java/games/strategy/net/nio/Decoder.java	67.64% <0%> (-0.99%)	24% <0%> (-1%)
...tegy/triplea/oddsCalculator/ta/OddsCalculator.java	43.88% <0%> (-0.32%)	13% <0%> (ø)
...rc/main/java/games/strategy/net/nio/NioWriter.java	70.58% <0%> (+3.36%)	21% <0%> (ø)	⬇️

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