After resizing traefik does not extend units to more backends

Scenario
- bootstrap with --accept-defaults
- add node with just control and compute role
- add node with just control and compute role

sunbeam cluster resize
and wait for the end of it

monitor api with
while true; do openstack server list && echo OK; done

kill keystone-0 pod
and it takes 1min around to have the API back

Seems that Traefik loadbalancer got just one server backend

ubuntu@node08:~$ kubectl exec -n openstack -c traefik -t traefik-0 -- cat /opt/traefik/juju/juju_ingress_
ingress_49_keystone.yaml
http:
….
     domains:
     - main: 10.20.21.12
       sans:
       - '*.10.20.21.12'
  services:
 juju-openstack-keystone-service:
   loadBalancer:
     servers:
     - url: http://keystone-0.keystone-endpoints.openstack.svc.cluster.local:5000

and that is true also for traefik-1 and traefik-2