fix: create control files only when needed

Summary:
This way the control directory is only created when a control file becomes
necessary. In case of default values control files are without information.
These files are then deleted.

FIXED-IN: 5.17.3

Test Plan:
Started Wayland session without writing a file and gets created when control
needs to be written.

Reviewers: Plasma

Subscribers: davidedmundson, plasma-devel

Tags: Plasma

Differential Revision: https://phabricator.kde.org/D25020