Fix magnum api dimensions

Change-Id: Ibb7d6981d9d7fed2293af6533e54fb9c768cace6
Closes-Bug: #1784497

ansible/roles/magnum/defaults/main.yml

@@ -14,7 +14,7 @@ magnum_services:
       - "/etc/localtime:/etc/localtime:ro"
       - "{{ kolla_dev_repos_directory ~ '/magnum/magnum:/var/lib/kolla/venv/lib/python2.7/site-packages/magnum' if magnum_dev_mode | bool else '' }}"
       - "kolla_logs:/var/log/kolla/"
-    dimensions: "{{ magnum_api }}"
+    dimensions: "{{ magnum_api_dimensions }}"
   magnum-conductor:
     container_name: magnum_conductor
     group: magnum-conductor