use node['fqdn'] rather than node['ipaddress']

It's better to use FQDNs here, because this is what will be shown in the clone URLs for example. 

For vagrant, the FQDNs are probably not set up, so we need to use the IP address here. This is not included in this PR, but tracked in vogelb/cookbooks-gitlab#18

With this PR:
* use `node['fqdn']` instead of `node['ipdaddress']`
* bind to `*:80` in nginx config and set `server_name` to FQDN
* assume gitlab-shell can access api via localhost