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