Treat deleted images as nonexistent on create

Refs #1986

snf-cyclades-app/synnefo/api/util.py

@@ -190,7 +190,7 @@ def get_backend_image(image_id, owner):
     backend = ImageBackend(owner.uniq)
     try:
         image = backend.get_image(image_id)
-        if not image:
+        if not image or image['deleted_at']:
             raise ItemNotFound('Image not found.')
         return image
     finally: