Allow object versioning for ceph-rgw

Object versioning test[1] is required for RefStack test suite.
Swift has enabled it by default[2].
It is also needed for ceph-rgw.

[1]
tempest.api.object_storage.test_object_version.ContainerTest.test_versioned_container
[2] https://review.openstack.org/#/c/517281/

Related-Bug: #1729583
Change-Id: If89636f77d87bab75e8e7bcf16cc784e83184bc6

ansible/roles/ceph/templates/ceph.conf.j2

@@ -40,6 +40,7 @@ rgw_keystone_admin_project = service
 rgw_keystone_admin_domain = default
 rgw_keystone_api_version = 3
 rgw_keystone_accepted_roles = admin, {{ keystone_default_user_role }}
+rgw_swift_versioning_enabled = true
 {% endif %}
 keyring = /etc/ceph/ceph.client.radosgw.keyring
 log file = /var/log/kolla/ceph/client.radosgw.gateway.log