update vncserver_listen configuration

[Daniel RJ Rooke]

Please see puppet-nova Bug #1660099 for background

Setting vncserver_listen to 0.0.0.0 is no longer necessary for live migration. If possible, please remove or update this section from puppet-tripleo/manifests/profile/base/nova/compute/libvirt.pp

    # TODO(emilien): Some work needs to be done in puppet-nova to separate nova-compute config
    # when running libvirt and libvirt itself, so we allow micro-services deployments.
    if str2bool(hiera('nova::use_ipv6', false)) {
      $vncserver_listen = '::0'
    } else {
      $vncserver_listen = '0.0.0.0'
    }

We would like to set vncserver_listen to the internalapi port on our systems similar to nova::compute::vncserver_proxyclient_address although I'm not sure this is correct for all.

until mitaka, this section appears to be located in tripleo-heat-templates/puppet/manifests/overcloud_compute.pp