Revert "Detach before setting the d pointer"

Summary:
This reverts commits 04cc49c7 as well
as the follow-up partial fix c32c8d00

The whole internal data sync'ing design of the KNewStuff core library
relies on EntryInternal instances explicitely sharing the data.
Changing only EntryInternal to implicitly shared data broke things.
And changed behaviour of that class also for any 3rd-party consumers.

BUG: 386156

Reviewers: whiting, leinir, apol

Reviewed By: leinir

Subscribers: #frameworks

Tags: #frameworks

Differential Revision: https://phabricator.kde.org/D9012