fix(user-data): use $private_ipv4 for etcd/fleet
fix(user-data): use $private_ipv4 for etcd/fleet

All etcd/fleet communication should be private, so have etcd/fleet
only listen on private IPs. Remote fleetctl still works, as it uses
an SSH tunnel. There's really no reason to ever use $public_ipv4.

deis/workflow,deis/workflow,deis/workflow