Make MetaDataUpdate auto-closeable

And convert users to instantiate it in try-with-resource blocks.

Change-Id: Ief1a42ccbf4b3d943a7987b2c9b8077175695515

gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/git/AbstractPushForReview.java

@@ -83,11 +83,8 @@ public abstract class AbstractPushForReview extends AbstractDaemonTest {
   }
 
   private void saveProjectConfig(ProjectConfig cfg) throws Exception {
-    MetaDataUpdate md = metaDataUpdateFactory.create(project);
-    try {
+    try (MetaDataUpdate md = metaDataUpdateFactory.create(project)) {
       cfg.commit(md);
-    } finally {
-      md.close();
     }
   }