[wayland] Fix teardown order
Summary:
Valgrind flags an error on teardown.
EventQueue has a pointer to ConnectionThread internally
Registry has a pointer to the EventQueue internally
teardown order needs to be
Registry
EventQueue
Connection
registry was explicitly deleted before connectionthread already, we just
need to put event queue in the right place.
Test Plan: Ran kwin_wayland nested in valgrind
Reviewers: KWin, cblack, apol
Reviewed By: cblack, apol
Subscribers: zzag, apol, kwin
Tags: KWin
Differential Revision: https://phabricator.kde.org/D28668