Fix neutron rolling upgrade

Services were being passed as a JSON list, then iterated over in the
neutron-server container's extend_start.sh script like this:

['neutron-server'
'neutron-fwaas'
'neutron-vpnaas']

I'm not actually sure why we have to specify services explicitly, it
seems liable to break if we have other plugins that need migrating.

Change-Id: Ic8ce595793cbe0772e44c041246d5af3a9471d44

ansible/roles/neutron/tasks/rolling_upgrade.yml

@@ -19,7 +19,7 @@
       KOLLA_UPGRADE:
       NEUTRON_DB_EXPAND:
       KOLLA_CONFIG_STRATEGY: "{{ config_strategy }}"
-      NEUTRON_ROLLING_UPGRADE_SERVICES: "{{ neutron_rolling_upgrade_services }}"
+      NEUTRON_ROLLING_UPGRADE_SERVICES: "{{ neutron_rolling_upgrade_services | join(' ') }}"
     image: "{{ neutron_server.image }}"
     labels:
       UPGRADE:
@@ -76,7 +76,7 @@
       KOLLA_UPGRADE:
       NEUTRON_DB_CONTRACT:
       KOLLA_CONFIG_STRATEGY: "{{ config_strategy }}"
-      NEUTRON_ROLLING_UPGRADE_SERVICES: "{{ neutron_rolling_upgrade_services }}"
+      NEUTRON_ROLLING_UPGRADE_SERVICES: "{{ neutron_rolling_upgrade_services | join(' ') }}"
     image: "{{ neutron_server.image }}"
     labels:
       UPGRADE: