Move nova online migrations to nova-conductor

With multi-cell we can have stacks with no nova-api so the nova database
operations must be coupled to nova-conductor, not nova-api.

Change-Id: I27aa62d00b77ca7ff61bb31c6f396f03e148a144
Closes-bug: #1883098

deployment/nova/nova-api-container-puppet.yaml

@@ -495,15 +495,6 @@ outputs:
             - step|int == 4
       host_prep_tasks: {get_attr: [NovaApiLogging, host_prep_tasks]}
       external_upgrade_tasks:
-        - when: step|int == 1
-          block:
-            - name: Online data migration for Nova
-              command: "{{ container_cli }} exec nova_api nova-manage db online_data_migrations"
-              delegate_to: "{{ groups['nova_api'][0] }}"
-              become: true
-              tags:
-                - online_upgrade
-                - online_upgrade_nova
         - when:
             - step|int == 1
           tags:

deployment/nova/nova-conductor-container-puppet.yaml

@@ -203,6 +203,15 @@ outputs:
                 persistent: yes
                 state: yes
       external_upgrade_tasks:
+        - when: step|int == 1
+          block:
+            - name: Online data migration for Nova
+              command: "{{ container_cli }} exec nova_conductor nova-manage db online_data_migrations"
+              delegate_to: "{{ groups['nova_conductor'][0] }}"
+              become: true
+              tags:
+                - online_upgrade
+                - online_upgrade_nova
         - when:
             - step|int == 1
           tags: