Make sure previously loaded transports are tried last

[ron-murhammer]

Fixes issue reported here: https://forums.triplea-game.org/topic/493/total-world-war-december-1941-beta-2-8-0-3/163

Bug
After an amphibious assault, transports that didn't unload any units aren't able to be loaded in NCM (see attached game where Germany can't load in SZ27):
1522769365231-tww-krautz-3.zip

Background
This logic was removed about 2 years ago when transport loading was enhanced as it didn't appear to be needed but actually is needed in some rare cases: https://github.com/triplea-game/triplea/pull/647/files#diff-9e673fd7f1882639b0d1e43323f11c53L142

[codecov-io]

Codecov Report

Merging #3344 into master will decrease coverage by <.01%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##             master    #3344      +/-   ##
============================================
- Coverage     21.93%   21.92%   -0.01%     
+ Complexity     5893     5890       -3     
============================================
  Files           834      834              
  Lines         72088    72088              
  Branches      11640    11640              
============================================
- Hits          15809    15805       -4     
- Misses        54190    54192       +2     
- Partials       2089     2091       +2

Impacted Files	Coverage Δ	Complexity Δ
...es/strategy/triplea/delegate/TransportTracker.java	68.5% <ø> (ø)	40 <0> (ø)	⬇️
...va/games/strategy/triplea/util/TransportUtils.java	43.31% <100%> (ø)	18 <0> (ø)	⬇️
...rategy/triplea/attachments/UnitTypeComparator.java	46.15% <0%> (-7.7%)	12% <0%> (-1%)
.../strategy/triplea/odds/calculator/DummyPlayer.java	35.22% <0%> (-1.14%)	9% <0%> (-1%)
.../src/main/java/games/strategy/net/nio/Decoder.java	72.82% <0%> (-1.09%)	24% <0%> (-1%)

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[ron-murhammer]

Merging as minor change to address a bug.