GtkApplication does magic like ensuring that the application ID is unique and
there is only a single instance of each application running. We don't want nor
need that for the tests.
Signed-off-by: Uli Schlachter <psychon@znc.in>
Startup notification support in urxvt is optional while GTK always supports
startup notification. Thus, use the new GTK-based test client for the SN tests.
Fixes: https://github.com/awesomeWM/awesome/issues/848
Signed-off-by: Uli Schlachter <psychon@znc.in>