The add_device() check for g_udev_device_get_parent() was leaking (see
below). As this is actually used in create_device(), I'm passing it as
argument to avoid a second call to that function.
> 34,175 (1,080 direct, 33,095 indirect) bytes in 27 blocks are definitely lost in loss record 19,729 of 19,758
> at 0x4A7A337: g_type_create_instance (gtype.c:1907)
> by 0x4A61CAC: g_object_new_internal (gobject.c:1945)
> by 0x4A62C7C: g_object_new_with_properties (gobject.c:2114)
> by 0x4A63780: g_object_new (gobject.c:1785)
> by 0x5EA5A6A: _g_udev_device_new (gudevdevice.c:132)
> by 0x4B6D24: add_device (gsd-device-manager.c:447)
> by 0x4B6FBF: gsd_device_manager_init (gsd-device-manager.c:517)
> by 0x4A7A288: g_type_create_instance (gtype.c:1929)
> by 0x4A61CAC: g_object_new_internal (gobject.c:1945)
> by 0x4A62C7C: g_object_new_with_properties (gobject.c:2114)
> by 0x4A63780: g_object_new (gobject.c:1785)
> by 0x4B7075: gsd_device_manager_get (gsd-device-manager.c:533)
dac8fd64cd