Fix Defaults not being set properly in Breeze window decoration settings for 'Draw a circle around close button'

Summary: This fixes a small bug in the Breeze window decoration settings where clicking on 'Defaults' did nothing to change 'Draw a circle around close button' . This patch now causes 'Draw a circle around close button' to default correctly.

Reviewers: Breeze, hpereiradacosta

Reviewed By: hpereiradacosta

Subscribers: ngraham, plasma-devel

Tags: Plasma

Differential Revision: https://phabricator.kde.org/D28087