zun: set docker api version to 1.24

Kolla is using Docker API version 1.24 but the default is 1.26
in Zun. We need to configure it to 1.24 so that Zun and Kolla
can work together.

Partial-Bug: #1782055
Change-Id: I072dccc06fe35dccf25068ef0ca8f39cad9fdc60

ansible/roles/zun/templates/zun.conf.j2

@@ -110,3 +110,6 @@ policy_file = {{ zun_policy_file }}
 wsproxy_host = {{ api_interface_address }}
 wsproxy_port = {{ zun_wsproxy_port }}
 base_url = ws://{{ kolla_external_fqdn }}:{{ zun_wsproxy_port }}
+
+[docker]
+docker_remote_api_version = 1.24