message: rabbitmq start up does this for us.
diff: #!/bin/sh
  -# copy from configmap to empty volume
  -cp -v /etc/rabbitmq/config/* /etc/rabbitmq/;
  -
  -#erlang cookie needs to be the same on all hosts,
  -echo "$ERLANG_COOKIE" > /var/lib/rabbitmq/.erlang.cookie;
  -chmod 600 /var/lib/rabbitmq/.erlang.cookie;
  -
  # clustering uses full hostnames, generate those
  echo NODENAME=rabbit@${HOSTNAME}.${SERVICE_NAME}.${POD_NAMESPACE}.svc.cluster.local > /etc/rabbitmq/rabbitmq-env.conf
  echo cluster_formation.k8s.hostname_suffix=.${SERVICE_NAME}.${POD_NAMESPACE}.svc.cluster.local >> /etc/rabbitmq/rabbitmq.conf
  