Magnum endpoint should not be versioned in service catalog

[Drago]

The best practice for service endpoints is for them to be unversioned. According to [1]:

> Querying type=’volume’ in any service catalog on any cloud returns an unversioned URL for that service. This is a contract we can depend on.

According to [2]:

> This should be unversioned base URL for an API. Good examples include https://identity.example.com:35357/ and https://keystone.example.com/.

> Conversely, https://identity.example.com:35357/v2.0/ is an unfortunate example because it directs all clients to connect to a versioned endpoint, regardless of which API versions they understand. This makes it hard for services to do any sort of API versioning, and for clients to dynamically discover additional available versions.

In magnum's devstack plugin, this is not the case. "v1" is appended to the endpoint [3]:

    get_or_create_endpoint $magnum_service \
        "$REGION_NAME" \
        "$MAGNUM_SERVICE_PROTOCOL://$MAGNUM_SERVICE_HOST:$MAGNUM_SERVICE_PORT/v1" \
        "$MAGNUM_SERVICE_PROTOCOL://$MAGNUM_SERVICE_HOST:$MAGNUM_SERVICE_PORT/v1" \
        "$MAGNUM_SERVICE_PROTOCOL://$MAGNUM_SERVICE_HOST:$MAGNUM_SERVICE_PORT/v1"

[1] http://specs.openstack.org/openstack/openstack-specs/specs/service-catalog.html#a-vision-of-the-ideal-service-catalog
[2] http://dolphm.com/openstack-keystone-service-catalog/
[3] https://github.com/openstack/magnum/blob/ed173776caa0a60a11e227f91d15615d4c6ec8e7/devstack/lib/magnum#L115-L117