Comment 4 for bug 1808595

I found a problem related to this method [1] in [2]. Could be useful to, instead of retrieving the first IP available in the network, retrieve a random one.

[1] https://github.com/openstack/neutron/blob/a63f34474874ff1966cc42d3f437888d4c5813f8/neutron/tests/fullstack/base.py#L128
[2] https://5447eebf83bcd6fc5a63-dc6e15462e9da95e02ee0e042cb47d52.ssl.cf2.rackcdn.com/670177/10/check/neutron-fullstack/83775b4/testr_results.html.gz