RabbitMQ: add server_name_indication to the federation parameters
    
    The Federation plugin uses an AMQP client that verifies that the
    hostname it's connecting to is the right one. Our RabbitMQ server
    TLS certificates only have the "public" name as Subject Alternative Name
    and in that case apparently the client does not check the CN. Therefore
    this changeset sets the client parameter to expect the "public" name in
    the certificate.
    
    Signed-off-by: Aurélien Bompard <aurelien@bompard.org>