defaultiface: Fix leak in test

https://bugzilla.gnome.org/show_bug.cgi?id=711779
diff --git a/tests/gobject/defaultiface.c b/tests/gobject/defaultiface.c
index 62a0d64..e00cb73 100644
--- a/tests/gobject/defaultiface.c
+++ b/tests/gobject/defaultiface.c
@@ -143,8 +143,9 @@
 test_dynamic_iface (void)
 {
   TestDynamicIfaceClass *dynamic_iface;
+  GTypeModule *module;
 
-  test_module_new (module_register);
+  module = test_module_new (module_register);
 
   /* Not loaded until we call ref for the first time */
   dynamic_iface = g_type_default_interface_peek (TEST_TYPE_DYNAMIC_IFACE);
@@ -181,6 +182,8 @@
 #if 0
   g_assert (!dynamic_iface_init);
 #endif
+
+  g_object_unref (module);
 }
 
 int