sometimes it is needed to use other than `openstack` CLI clients
or older versions of those in bootstrap/other scripts that do not
understand the OS_INTERFACE env var, and instead use the
OS_ENDPOINT_TYPE var (and --os-endpoint-type CLI arg) for the same
purpose.
Example is `neutron` command from python-neutronclient package.
Change-Id: I0fb7d1e9612391e8632d775b91848d3c834b9bd2
5dc986aa5f