cluster-management: add etcdctl env vars

Add env vars to make etcdctl feel the same locally, but use the remote etcd cluster. To do this we need to configure the etcd machine's addrs in the Easy Development example.

cc: @bcwaldon 
The "sync" feature of etcdctl (actually go-etcd) downloads a list of "client" endpoints from one of the "peers" defined in ETCDCTL_PEERS/--peers. This new list replaces the local set of "peers". Yes, the terms are being used incorrectly here.

The peer-addr flag in the etcd config above is defining on what interface the "peer" endpoint should be made available. This does not impact the "client" endpoints that end up getting synced by etcdctl.