Make docker network configurable
Make docker network configurable

The default docker0 address conflicts with the InternalApiNetCidr value
set in environments/network-environment.yaml. We should provide a way
to make the docker network configurable.

Change-Id: Ie803b33c93b931f7fefb87b6833eb22fd59cd92d
Related-Bug: #1726773

openstack/puppet-tripleo,openstack/puppet-tripleo,openstack/puppet-tripleo