waitIndex is not working

start a one member cluster 
base
```
./etcd
```

set key and wait from a previous index
```
curl http://127.0.0.1:4001/v2/keys/foo -XPUT -d value=bar
{"action":"set","node":{"key":"/foo","value":"bar","modifiedIndex":4,"createdIndex":4}}
curl http://127.0.0.1:4001/v2/keys/foo?wait=true\&waitIndex=1
... hangs forever
```