Refresh volume alloc/capacity when dumping XML.

src/storage_driver.c

@@ -1389,6 +1389,10 @@ storageVolumeGetXMLDesc(virStorageVolPtr obj,
     if ((backend = virStorageBackendForType(pool->def->type)) == NULL)
         goto cleanup;
 
+    if (backend->refreshVol &&
+        backend->refreshVol(obj->conn, pool, vol) < 0)
+        goto cleanup;
+
     ret = virStorageVolDefFormat(obj->conn, pool->def, vol);
 
 cleanup: