It appears to be that the Neutron Segment plugin needs to instantiate a
placement service client which requires credentials and other connection
details:
https://opendev.org/openstack/neutron/src/branch/stable/ussuri/neutron/services/segments/plugin.py#L188
Otherwise, the following exception can be seen periodically in the
Neutron log:
keystoneauth1.exceptions.auth_plugins.MissingAuthPlugin:
An auth plugin is required to determine endpoint URL
Change-Id: I480292a1c74c376db5c9797b1fcc8469e0e5507a