feat: add barrier mode support for VW

[eisber]

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[mhamilton723]

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[codecov]

Codecov Report

Merging #832 into master will increase coverage by 0.01%.
The diff coverage is 91.66%.

@@            Coverage Diff             @@
##           master     #832      +/-   ##
==========================================
+ Coverage   85.15%   85.16%   +0.01%     
==========================================
  Files         186      186              
  Lines        8573     8582       +9     
  Branches      512      519       +7     
==========================================
+ Hits         7300     7309       +9     
  Misses       1273     1273              

Impacted Files	Coverage Δ
...a/com/microsoft/ml/spark/vw/VowpalWabbitBase.scala	89.04% <91.66%> (-0.01%)	⬇️
...om/microsoft/ml/spark/core/utils/ClusterUtil.scala	68.75% <0.00%> (+2.08%)	⬆️

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[eisber]

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[mhamilton723]

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[eisber]

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[eisber]

/azp run

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