ENYO-3074: Fixed issue with tap event being sent after dragfinish event

Issue
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A `tap` event will be sent after a `dragfinish` event in a dragging context.

Fix
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The synthesized `dragfinish` event provides a `preventTap` method, but only `enyo.Scroller` controls were utilizing this method. The `dragfinish` synthesizer code now always initiates a `preventTap` directly, as this will only be triggered in a dragging context. As a result, `dragfinish` no longer provides a `preventTap` method and calls to `preventTap` have been removed from subsequent handlers i.e. `enyo.Scroller`'s own `dragfinish` handler.

Enyo-DCO-1.1-Signed-off-by: Aaron Tam <aaron.tam@lge.com>