1. volume server auto detect clustered master nodes

2. remove operation package dependency on storage

go/util/http_util.go

@@ -21,3 +21,18 @@ func Post(url string, values url.Values) ([]byte, error) {
 	}
 	return b, nil
 }
+
+func Get(url string) ([]byte, error) {
+	r, err := http.Get(url)
+	if err != nil {
+		glog.V(0).Infoln("getting ", url, err)
+		return nil, err
+	}
+	defer r.Body.Close()
+	b, err := ioutil.ReadAll(r.Body)
+	if err != nil {
+		glog.V(0).Infoln("read get result from", url, err)
+		return nil, err
+	}
+	return b, nil
+}