[PC3] Complete plasma progress bar animation

Summary:
Otherwside if we toggle indeterminate the bar resizes to 50% of the view
and X stops on the current value of the animation. Resulting in
something that looks super odd.

Test Plan: Plasma Components manual uit test looks sane

Subscribers: kde-frameworks-devel

Tags: Frameworks

Differential Revision: https://phabricator.kde.org/D25927