Object is supposed to be freed by invoking obj->free, and not
obj->instance_finalize. This would lead to use-after-free followed by
double free in object_unref/object_finalize.

Signed-off-by: Daniil Tatianin <d-tatianin@yandex-team.ru>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20211117142349.836279-1-d-tatianin@yandex-team.ru>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>