Reset indentation variable when stream is resetted (#525)

Author: dr0i

metafacture-biblio/src/main/java/org/metafacture/biblio/marc21/MarcXmlEncoder.java

@@ -277,6 +277,7 @@ protected void onResetStream() {
             writeFooter();
         }
         sendAndClearData();
+        indentationLevel = 0;
         atStreamStart = true;
     }