Fix two instances of immutable collections being used to initialize List arguments

[droazen]

Barclay can't currently handle immutable collections in @Argument values due to
#4702

Tests for these arguments are coming in a separate, larger branch, but I
wanted to get the fixes in first since it's such a simple fix.

[jonn-smith]

Looks good to me.

[codecov-io]

Codecov Report

Merging #4703 into master will increase coverage by 0.02%.
The diff coverage is n/a.

@@              Coverage Diff               @@
##              master     #4703      +/-   ##
==============================================
+ Coverage     79.853%   79.873%   +0.02%     
- Complexity     17340     17348       +8     
==============================================
  Files           1074      1074              
  Lines          62956     63104     +148     
  Branches       10189     10231      +42     
==============================================
+ Hits           50272     50403     +131     
- Misses          8701      8712      +11     
- Partials        3983      3989       +6

Impacted Files	Coverage Δ	Complexity Δ
...notyper/GenotypeCalculationArgumentCollection.java	100% <ø> (ø)	2 <0> (ø)	⬇️
...otypecaller/HaplotypeCallerArgumentCollection.java	100% <ø> (ø)	2 <0> (ø)	⬇️
...utils/smithwaterman/SmithWatermanIntelAligner.java	50% <0%> (-30%)	1% <0%> (-2%)
...oadinstitute/hellbender/tools/LeftAlignIndels.java	0% <0%> (ø)	0% <0%> (ø)	⬇️
...org/broadinstitute/hellbender/tools/ClipReads.java	91.958% <0%> (+1.573%)	36% <0%> (+1%)	⬆️
...lbender/tools/walkers/RevertBaseQualityScores.java	95.455% <0%> (+2.597%)	8% <0%> (+2%)	⬆️
...lbender/tools/walkers/rnaseq/SplitNCigarReads.java	90.972% <0%> (+3.472%)	39% <0%> (+5%)	⬆️
...ute/hellbender/tools/walkers/UnmarkDuplicates.java	93.75% <0%> (+3.75%)	7% <0%> (+2%)	⬆️