Fix several warnings during puppet-apply.

This fixes several errors from puppet:
* [107.170.234.125] Warning: Variable access via 'name' is deprecated. Use '@name' instead. template[/tmp/supply_drop/puppet/modules/nginx/templates/upstream.erb]:1
* [107.170.234.125] (at /tmp/supply_drop/puppet/modules/nginx/templates/upstream.erb:1:in `result')
* [107.170.234.125] Warning: Variable access via 'members' is deprecated. Use '@members' instead. template[/tmp/supply_drop/puppet/modules/nginx/templates/upstream.erb]:2
* [107.170.234.125] (at /tmp/supply_drop/puppet/modules/nginx/templates/upstream.erb:2:in `result')
* [107.170.234.125] Warning: Variable access via 'match_type' is deprecated. Use '@match_type' instead. template[/tmp/supply_drop/puppet/modules/nginx/templates/vhost/vhost_location_proxy.erb]:1
* [107.170.234.125] (at /tmp/supply_drop/puppet/modules/nginx/templates/vhost/vhost_location_proxy.erb:1:in `result')
* [107.170.234.125] Warning: Variable access via 'proxy' is deprecated. Use '@proxy' instead. template[/tmp/supply_drop/puppet/modules/nginx/templates/vhost/vhost_location_proxy.erb]:2
* [107.170.234.125] (at /tmp/supply_drop/puppet/modules/nginx/templates/vhost/vhost_location_proxy.erb:2:in `result')
* [107.170.234.125] Warning: Variable access via 'proxy_set_headers' is deprecated. Use '@proxy_set_headers' instead. template[/tmp/supply_drop/puppet/modules/nginx/templates/vhost/vhost_location_proxy.erb]:16
* [107.170.234.125] (at /tmp/supply_drop/puppet/modules/nginx/templates/vhost/vhost_location_proxy.erb:16:in `result')
* [107.170.234.125] Warning: Variable access via 'listen_ip' is deprecated. Use '@listen_ip' instead. template[/tmp/supply_drop/puppet/modules/nginx/templates/vhost/vhost_header.erb]:2
* [107.170.234.125] (at /tmp/supply_drop/puppet/modules/nginx/templates/vhost/vhost_header.erb:2:in `result')
* [107.170.234.125] Warning: Variable access via 'server_names' is deprecated. Use '@server_names' instead. template[/tmp/supply_drop/puppet/modules/nginx/templates/vhost/vhost_header.erb]:8
* [107.170.234.125] (at /tmp/supply_drop/puppet/modules/nginx/templates/vhost/vhost_header.erb:8:in `result')
* [107.170.234.125] Warning: Variable access via 'www_root' is deprecated. Use '@www_root' instead. template[/tmp/supply_drop/puppet/modules/nginx/templates/vhost/vhost_header.erb]:10
* [107.170.234.125] (at /tmp/supply_drop/puppet/modules/nginx/templates/vhost/vhost_header.erb:10:in `result')

I haven't audited for other non-ivar variable accesses; this only fixes
the templates that my installation happens to use.