middleware/etcd: Use the correct endpoint

The endpoint for etcd as wrongly set if a proxy was configured.
Clean up some documentation in the process as well.

middleware/etcd/setup_test.go

@@ -2,9 +2,6 @@
 
 package etcd
 
-// etcd needs to be running on http://127.0.0.1:2379
-// *and* needs connectivity to the internet for remotely resolving names.
-
 import (
 	"encoding/json"
 	"sort"