If you are using provider networking, and have IP_VERSION set to include
IPv6 (which we do by default) - you must set the required variables.
If you do not want this behavior, set IP_VERSION=4
This arose from a third party CI system which was configured[1] to have
provider networking, but would explode when hitting the router IPv6
setup step[2] since there was no IPv6 subnet created, and IPV6_SUBNET_ID
would be empty, causing a python-neutronclient error and causing
stack.sh to exit.
[1]: http://paste.openstack.org/show/508710/
[2]: c35110e7c5/lib/neutron_plugins/services/l3 (L320)
Change-Id: I267799b62284c3086ed7c3e2d8a9cbadb9ddcd60
e34ec9901e