Comment 0 for bug 1324598

This change https://review.openstack.org/88036 added the definition of a section in the nova.conf mustache template file to enable the passthrough settings.

The template as-is has two problems:
- the comment are not rendered at all. If there is comment in the passthrough configuration the resulting nova-conf file instead of reporting the comment it reports "repeats for each section "
- as all variables are HTML-escaped by default in a mustache template we want to use the triple braces to rendere unscaped HTML

here an example that shows what I described above:
JSON
{
  "nova": {
    "config": [
      {"section": "DEFAULT",
       "comment": "this is a comment",
       "values": [
          {
            "option": "snapshots_directory",
            "value": "/mnt/state/var/lib/nova/tmp"
          }
        ]
      }
    ]
  }
}

Output
 repeats for each section
[DEFAULT]
snapshots_directory=/mnt/state/var/lib/nova/tmp