This patches fixes the following error when testing ModemManager with
glib < 2.36, which still requires g_type_init() to be called:
TEST: test-service-generic... (pid=20166)
/MM/Service/Generic:
(/work/ModemManager/plugins/.libs/lt-test-service-generic:20166): GLib-GObject-CRITICAL **: gtype.c:2720: You forgot to call g_type_init()
FAIL