Add sample environment file to document usage of predictable IPs
Add sample environment file to document usage of predictable IPs

This change adds a sample environment file which documents how to
assign to controllers a predictable IP on each network.

Change-Id: I5be21428c66c82488af8e0240c1614ac3b9b55f0

trozet/opnfv-tht,openstack/tripleo-heat-templates,openstack/tripleo-heat-templates,bcrochet/tripleo-heat-templates,trozet/opnfv-tht,bcrochet/tripleo-heat-templates,trozet/opnfv-tht,dprince/tripleo-heat-templates,dprince/tripleo-heat-templates,bcrochet/tripleo-heat-templates