Commit 390fab8da43339e04dae511b5a8bf4a6235cb8ea changed how nova.conf is
generated via the tox genconfig target, however, it fails to load the
'versionutils' namespace entry from nova-config-generator.conf since
nova.openstack.common.versionutils does not exist. The versionutils
module is now in oslo.utils rather than oslo-incubator. That was removed
in commit 2233675941c075c77208ecf379fc439c87d6fc5b.
Closes-Bug: #1469197
Change-Id: Id182469c4072827f987728f4e72933f97c8f1112