KConfig: handle directory symlinks correctly.

Summary:
When /home is a symlink, for instance (as is often the case on FreeBSD),
group deletion would fail because KConfig was comparing non-canonical
paths with canonical-paths:

QDEBUG : KConfigTest::testDelete() Comparing "/home/adridg/.qttest/config/
kconfigtest_subdir/kconfigtest" and "/usr/home/adridg/.qttest/config/
kconfigtest_subdir/kconfigtest"

Test Plan:
mkdir /tmp/derp; ln -s /tmp/derp /tmp/drop
HOME=/tmp/derp bin/kconfigtest testDelete # Success
HOME=/tmp/drop bin/kconfigtest testDelete # Fail

Reviewers: adridg, arichardson, apol

Reviewed By: apol

Subscribers: kde-frameworks-devel

Tags: Frameworks

Differential Revision: https://phabricator.kde.org/D14927