Summary:
if the control height is
2*Metrics::LineEdit_FrameWidth + option->fontMetrics.height()
it means that "it just fits", therefore still draw the frame

the qqc2-desktop style uses that logic to get default line edit
heights, so they all got disabled by just one pixel

Test Plan: tested qwidget and qml apps

Reviewers: #plasma, hpereiradacosta

Reviewed By: hpereiradacosta

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D8160