Summary:
The test executable "kill" freezes itself after 1ms, supposedly after
showing a window.
However showing a window is not syncronous on wayland, it's illegal to
map a buffer before getting a configure event from the server.
This patch removes any potential for a race by having the server tell
our test executable when to freeze.
Test Plan: Test still passed
Reviewers: #kwin
Subscribers: kwin
Tags: #kwin
Differential Revision: https://phabricator.kde.org/D19406
768e5fb7f4