fix(dropdown): Keyboard selection of toggle causes selection of parent

[jessiehuff]

This was noticed in the context of data list selectable rows and selectable cards. If the action/toggle was selected by keyboard, the entire parent (the row or card) would be selected.

What: Closes #3617

[patternfly-build]

PF3 preview: https://patternfly-react-pr-3816-pf3.surge.sh
PF4 preview: https://patternfly-react-pr-3816.surge.sh
A11y report: https://patternfly-react-pr-3816-coverage.surge.sh

[codecov-io]

Codecov Report

Merging #3816 into master will decrease coverage by 0.01%.
The diff coverage is 33.33%.

@@            Coverage Diff             @@
##           master    #3816      +/-   ##
==========================================
- Coverage      71%   70.98%   -0.02%     
==========================================
  Files         785      785              
  Lines       10638    10641       +3     
  Branches     2314     2316       +2     
==========================================
+ Hits         7553     7554       +1     
- Misses       2655     2657       +2     
  Partials      430      430

Flag	Coverage Δ
#misc	95.45% <ø> (ø)	⬆️
#patternfly3	85.89% <ø> (ø)	⬆️
#patternfly4	60% <33.33%> (-0.02%)	⬇️

Impacted Files	Coverage Δ
...ly-4/react-core/src/components/Dropdown/Toggle.tsx	55.55% <0%> (-2.59%)	⬇️
...react-core/src/components/Dropdown/KebabToggle.tsx	93.33% <100%> (+0.47%)	⬆️

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[dlabrecq]

I've encountered similar problems in Cost Management where I had to catch the event myself and call event.preventDefault.