tests: Fix a double-close of a GSource in tests
This bug only gets triggered on BSD, because it calls recv_message()
with G_IO_HUP | G_IO_IN
. That takes two code paths in
recv_message()
, and ends up calling shutdown_source()
twice. The
second call causes a critical warning.
Fixes: https://gitlab.gnome.org/GNOME/glib/-/jobs/2004192
Signed-off-by: Philip Withnall pwithnall@endlessos.org