add net-id to example configs

This is a very minor addition to the example configs that includes the "net-id" directive to use with openstack clusters that run multiple networks (e.g. external and internal).

When running openstack with multiple networks and a net-id isn't specified the following error will occur during the compilation phase during a deploy:

<pre>
update:
Preparing package compilation

Compiling packages
  nginx/1: OpenStack API Bad Request (Multiple possible networks found, use a Network ID to be more specific.). Check task debug log for details. (00:00:02)
Error                   1/1 00:00:02

Error 100: OpenStack API Bad Request (Multiple possible networks found, use a Network ID to be more specific.). Check task debug log for details.
</pre>