Update thruk config for grafana

[rverchere]

Update thuk config to make grafana datasource works:

• Add "default_user_name=admin" in /etc/thruk/cgi.cfg or maybe a less critical account that can see informations

• Add Require ip 127.0.0.1 in /etc/httpd/conf.d/thruk.conf, after the require valid-user

These changes are already in the ansible roles, but not when using ISO Fresh Install.