ENYO-2996: fix initialization of showing property

On initialization of style, one-time CSS prioritization will
synchronize the showing property correctly so that they can
continue to be used interchangeably

Enyo-DCO-1.1-Signed-off-by: Cole Davis <cole.davis@lge.com>
Merge pull request #482 from enyojs/ENYO-2996

on initialization of style, one-time CSS prioritization will synchronize...

Reviewed-By: Ben Combee (ben.combee@lge.com)