Write public IP into private when there's no private
Write public IP into private when there's no private

devstack-gate multi-node depends on there always being a value in
private_v4 - even if that value is the public address. That's clearly
going to lead to confusion long term - but until we can rework it, this
should unbreak jobs that depend on that interface.

Change-Id: Icf52c9358cfe7c5103ce785027730e7c06c4429e

Tesora/tesora-nodepool,Tesora/tesora-nodepool,seandst/nodepool,seandst/nodepool