fix: Fix logistic regression error when passing "--link logistic"

[eisber]

fixes #642
updates to latest VW (required for link logistic fix)
fixes logistic regression unit test

[eisber]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[codecov]

Codecov Report

Merging #644 into master will decrease coverage by 21.58%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##           master     #644       +/-   ##
===========================================
- Coverage   76.77%   55.18%   -21.59%     
===========================================
  Files         224      171       -53     
  Lines        8963     7805     -1158     
  Branches      488      489        +1     
===========================================
- Hits         6881     4307     -2574     
- Misses       2082     3498     +1416

Flag	Coverage Δ
#python	100% <ø> (+52.15%)	⬆️
#scala	55.18% <100%> (-25.89%)	⬇️

Impacted Files	Coverage Δ
...a/com/microsoft/ml/spark/vw/VowpalWabbitBase.scala	85.81% <100%> (+0.19%)	⬆️
...microsoft/ml/spark/vw/VowpalWabbitClassifier.scala	86.36% <100%> (+4.54%)	⬆️
.../com/microsoft/ml/spark/lightgbm/TrainParams.scala	0% <0%> (-100%)	⬇️
...cala/com/microsoft/ml/spark/io/binary/Binary.scala	0% <0%> (-100%)	⬇️
.../microsoft/ml/spark/lightgbm/LightGBMBooster.scala	0% <0%> (-98.77%)	⬇️
...ql/execution/streaming/continuous/HTTPSinkV2.scala	0% <0%> (-96.56%)	⬇️
.../microsoft/ml/spark/lightgbm/LightGBMDataset.scala	0% <0%> (-96.16%)	⬇️
...om/microsoft/ml/spark/lightgbm/LightGBMUtils.scala	0% <0%> (-95.3%)	⬇️
.../execution/streaming/continuous/HTTPSourceV2.scala	0% <0%> (-92.6%)	⬇️
...a/com/microsoft/ml/spark/lightgbm/TrainUtils.scala	0% <0%> (-89.96%)	⬇️
... and 106 more

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[eisber]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).