RFC: Fix wayland backend initialisation
Otherwise it thinks outputs couldn't be created and it leaves.
Problem is that after this fix it crashes when it actually does things with:
kwin_wayland: /home/apol/devel/frameworks/kwin/composite.cpp:646: void KWin::Compositor::aboutToSwapBuffers(): Assertion `!m_bufferSwapPending' failed.
Test Plan: As said, it proceeds correctly and crashes elsewhere
Reviewers: KWin, davidedmundson
Reviewed By: KWin, davidedmundson
Subscribers: davidedmundson, kwin
Differential Revision: https://phabricator.kde.org/D19921