BHV-747: Do not animate slider when constrainToBgProgress is true and unclamped value is greater than bgProgress.

Enyo-DCO-1.1-Signed-off-by: Aaron Tam <aaron.tam@lge.com>
Streamline calculation of allowAnimation boolean.
Merge pull request #1150 from enyojs/BHV-747-aarontam

BHV-747: Do not animate slider when constrainToBgProgress is true and unclamped value is greater than bgProgress.