fix volume_layout bug, add new feature for volume etag write,filer pass through query params'

weed/server/filer_server_handlers_read.go

@@ -70,6 +70,13 @@ func (fs *FilerServer) GetOrHeadHandler(w http.ResponseWriter, r *http.Request,
 		return
 	}
 	u, _ := url.Parse(urlString)
+	q := u.Query()
+	for key, values := range r.URL.Query() {
+		for _, value := range values {
+			q.Add(key, value)
+		}
+	}
+	u.RawQuery = q.Encode()
 	request := &http.Request{
 		Method:        r.Method,
 		URL:           u,

weed/server/volume_server_handlers_write.go

@@ -42,6 +42,8 @@ func (vs *VolumeServer) PostHandler(w http.ResponseWriter, r *http.Request) {
 		ret.Name = string(needle.Name)
 	}
 	ret.Size = size
+	etag := needle.Etag()
+	w.Header().Set("Etag", etag)
 	writeJsonQuiet(w, r, httpStatus, ret)
 }