Example doesn't work without prerequisite openstack config

[Matt Verran]

This bug tracker is for errors with the documentation, use the following as a template and remove or add fields as you see fit. Convert [ ] into [x] to check boxes:

- [X] This doc is inaccurate in this way: The example cannot be completed as by default Openstack instances will not resolve 'app-worker-2' even if that is their instance name (this is true at least of RDO Packstack and devstack installs). Tutorial should link to tested process for local dns resolution (hint: https://docs.openstack.org/ocata/networking-guide/config-dns-int.html on its own doesn't work).

- [ ] This is a doc addition request.
- [ ] I have a fix to the document that I can paste below including example: input and output.

If you have a troubleshooting or support issue, use the following resources:

 - Ask OpenStack: http://ask.openstack.org
 - The mailing list: http://lists.openstack.org
 - IRC: 'openstack' channel on Freenode

-----------------------------------
Release: 0.1 on 2017-08-23 08:59
SHA: 833c20124e369adab292ae498f691ab45dbeab65
Source: https://git.openstack.org/cgit/openstack/api-site/tree/doc/source/scaling_out.rst
URL: https://developer.openstack.org/firstapp-libcloud/scaling_out.html

[Anne Gentle (annegentle)]

Nice find.