Stopy proxying etcd (localhost:4001) on https:/$MASTER_IP/etcd.

This is a small first step towards implementing the changes discussed in #443.
It removes the proxying of /etcd by the nginx proxy.  This is necessary in order to cleanly remove Basic Auth from the system entirely, in order to replace it with token-based auth.

I ran e2e locally, and basic.sh failed while guestbook.sh passed.
The fact that the more complex test passed makes me think the failure was due to flakiness.  So, I'm making the PR so travis can run e2e again.