Remove [neutron]/auth_strategy option in nova.conf

The [neutron]/auth_strategy has been removed,
read the information[1] to learn more.

[1] http://git.openstack.org/cgit/openstack/nova/tree/releasenotes/notes/remove-deprecated-neutron-options-5f3a782aa9082fb5.yaml

Closes-Bug: 1602171
Change-Id: Ide7ff9f36e89b8a091e5be3fb24ef210f9037e86

ansible/roles/nova/templates/nova.conf.j2

@@ -110,7 +110,6 @@ catalog_info = volume:cinder:internalURL
 
 [neutron]
 url = {{ internal_protocol }}://{{ kolla_internal_fqdn }}:{{ neutron_server_port }}
-auth_strategy = keystone
 metadata_proxy_shared_secret = {{ metadata_secret }}
 service_metadata_proxy = true