Add default index settings when parsing index for ODFE 1.10 (#206)

[jmazanec15]

Issue #, if available:
#204

Description of changes:
Cherry pick of #205

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[codecov]

Codecov Report

Merging #206 into opendistro-1.10 will increase coverage by 0.51%.
The diff coverage is 100.00%.

@@                  Coverage Diff                  @@
##             opendistro-1.10     #206      +/-   ##
=====================================================
+ Coverage              76.44%   76.95%   +0.51%     
- Complexity               301      302       +1     
=====================================================
  Files                     50       50              
  Lines                   1163     1189      +26     
  Branches                 100      100              
=====================================================
+ Hits                     889      915      +26     
  Misses                   225      225              
  Partials                  49       49              

Impacted Files	Coverage Δ	Complexity Δ
...ndistroforelasticsearch/knn/index/KNNSettings.java	83.47% <100.00%> (+1.48%)	27.00 <0.00> (ø)
...relasticsearch/knn/index/KNNVectorFieldMapper.java	77.85% <100.00%> (+2.85%)	15.00 <1.00> (+1.00)

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