Update replacing variable name

K-A patch [1] introduced a new variable ``docker_image_url`` to avoid
repeating ``docker_image_name_prefix`` variable.

Updating kolla-images.py accordingly.

[1] https://review.opendev.org/c/openstack/kolla-ansible/+/951747

Author: seunghun1ee

tools/kolla-images.py

@@ -315,7 +315,7 @@ def check_image_map(kolla_ansible_path: str):
     image_map = yaml.safe_load(image_map_str)
     image_var_re = re.compile(r"^([a-z0-9_]+)_image$")
     image_map = {
-        image_var_re.match(image_var).group(1): image.split("/")[-1].replace('{{ docker_image_name_prefix }}', '')
+        image_var_re.match(image_var).group(1): image.split("/")[-1].replace('{{ docker_image_url }}', '')
         for image_var, image in image_map.items()
     }
     # Filter out unsupported images.