Commit meta data changes to notedb when adding approvals on merge

When a change is merged, a SUBMIT approval is added to the change, but
this approval was not stored in notedb since the change update was not
committed.

This fixes several tests that were failing when notedb is enabled.

Change-Id: Ie58f600a69b815ff401ceab1d638c151178b3e7a
Signed-off-by: Edwin Kempin <ekempin@google.com>

gerrit-server/src/main/java/com/google/gerrit/server/git/MergeOp.java

@@ -1071,6 +1071,7 @@ public class MergeOp {
     } finally {
       db.rollback();
     }
+    update.commit();
     indexer.index(db, cd.change());
   }