BHV-2446: Check that focus has actually left the scroller before hiding scroll columns.

Issue
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When pressing a 5-way direction key inside a scroller (i.e. `moon.DataList`), the scroll columns will be hidden even if focus doesn't end up leaving the scroller.

Fix
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When the `onSpotlightContainerLeave` event is handled, we check that the currently spotted control is not the same control that was spotted when leaving the container.

Notes
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Can someone check my logic here - the `onSpotlightContainerLeave` event on the originating container is sent after the next control is spotted, as `onSpotlightContainerLeave` is dispatched via the `onSpotlightFocused` event of that container. This should always occur after `onSpotlightFocus` has spotted the next control, but I wanted to make sure there weren't any potential timing issues.

This PR is related to a Spotlight PR: https://github.com/enyojs/spotlight/pull/125

Enyo-DCO-1.1-Signed-off-by: Aaron Tam <aaron.tam@lge.com>