volume: compaction can cause readonly volumes

address https://github.com/chrislusf/seaweedfs/issues/1233

weed/server/volume_grpc_vacuum.go

@@ -51,6 +51,11 @@ func (vs *VolumeServer) VacuumVolumeCommit(ctx context.Context, req *volume_serv
 	} else {
 		glog.V(1).Infof("commit volume %d", req.VolumeId)
 	}
+	if err == nil {
+		if vs.store.GetVolume(needle.VolumeId(req.VolumeId)).IsReadOnly() {
+			resp.IsReadOnly = true
+		}
+	}
 
 	return resp, err