evas_object_image: fix cutout bug related with opaque object

Summary:
  condition:
  1. full size rect
  2. upper side, if there is same size image object and image object preload state is EVAS_IMAGE_PRELOADING.
  below rect cannot be rendered because upper image object was added to cutout area event though image object is not opaque.

  so fix opaque check function return false for opaque state of preloading image.

Reviewers: Hermet, raster

Subscribers: cedric, #reviewers, #committers

Tags: #efl

Differential Revision: https://phab.enlightenment.org/D7318

src/lib/evas/canvas/evas_object_image.c

@@ -2720,6 +2720,8 @@ evas_object_image_is_opaque(Evas_Object *eo_obj EINA_UNUSED,
     o->cur.opaque_valid = 0;*/
    Evas_Image_Data *o = type_private_data;
 
+   if (o->preload == EVAS_IMAGE_PRELOADING) return 0;
+
    if (o->cur->opaque_valid)
      {
         if (!o->cur->opaque) return 0;