'Versions.factory()' is deprecated in version 'Queens'
and was marked to be removed 'Rocky'.
This patch removes it and switches to use
neutron.pecan_wsgi.app.versions_factory instead.
In addition, neutron.api.versions is removed
because this deprecated module isn't used anywhere.
Change-Id: I08d1725a973c734b55771918915428377fb7d3b4