In the case of an assert, for example a wayland error Xwayland will
exit, but with an exitStatus of "normal exit".

We also trigger a shutdown should kwin encounter an error on the X11
side, this would be a clean exit from an XwaylandLauncher point of view.
It makes sense to try to restart.

Deliberate shutdown is handled by destroying the XwaylandLauncher. This
means it's not an issue for final kwin teardown.