It needs to be called as early as possible before unit tests
has a chance to import gtk.
Hopefully will fix random test failures we are seeing in buildbot.
This ensures the test itself is not recognized as a client
by the registry. I'm not sure how that happens since we are
not loading gtk, but it does. Not being a real gtk client with
a mainloop we wasn't answering dbus calls and causing the registry
to hang and fail.
