change kuryr default driver option name

kuryr changed driver option to default_driver

Ref: https://review.openstack.org/#/c/508778/

this change updates the template to apply the change.

Change-Id: I38669564a769bbe7b55386db5208a3341b15da9e

ansible/roles/kuryr/templates/kuryr.conf.j2

@@ -7,7 +7,7 @@ capability_scope = global
 bindir = /var/lib/kolla/venv/libexec/kuryr
 
 [binding]
-driver = kuryr.lib.binding.drivers.veth
+default_driver = kuryr.lib.binding.drivers.veth
 
 [neutron]
 auth_uri = {{ internal_protocol }}://{{ kolla_internal_fqdn }}:{{ keystone_public_port }}