fix build error

weed/server/volume_server_handlers_read.go

@@ -68,7 +68,7 @@ func (vs *VolumeServer) GetOrHeadHandler(w http.ResponseWriter, r *http.Request)
 	count, e := vs.store.ReadVolumeNeedle(volumeId, n)
 	glog.V(4).Infoln("read bytes", count, "error", e)
 	if e != nil || count < 0 {
-		glog.V(0).Infof("read %s error:", r.URL.Path, e)
+		glog.V(0).Infof("read %s error: %v", r.URL.Path, e)
 		w.WriteHeader(http.StatusNotFound)
 		return
 	}