Create a role which prepares xci for functest

Create a role which prepares xci for functest

Functest requires xci deployment to have:

- A public neutron network
- A subnet attached to the public neutron network
- The gateway from the subnet attached to one interface

The network and subnet creation are done via a script
instead of using Ansible OpenStack module in order to
get things working asap.

These three tasks are implemented in a role

This patch depends on a pending patch:

https://gerrit.opnfv.org/gerrit/#/c/39517/2

Change-Id: I0635227153087fd9e25b76f0859f82bf48bfb930
Signed-off-by: Manuel Buil <mbuil@suse.com>
Signed-off-by: Fatih Degirmenci <fatih.degirmenci@ericsson.com>