Unit Test for "Carousel: Only prevents default for ARROW_LEFT and ARROW_RIGHT keys" failed

Created by: Johann-S

See https://travis-ci.org/twbs/bootstrap/builds/186274719 + https://travis-ci.org/twbs/bootstrap/builds/186304707

Due to : https://github.com/twbs/bootstrap/blob/v4-dev/js/src/carousel.js#L244

X-Ref : https://github.com/twbs/bootstrap/pull/20907

/CC @bardiharborow , @matheusazzi