Set subject for commits on note branch when change/ps is created

Instead of using the default subject for commits on the note branch
which is

  Update patch set XX

be more specific when a change / patch set is created:

  Create change / Create patch set XX

These messages are consistent with the ones that are set by
ChangeRebuilder.

Change-Id: I26a0154f92d55fe594d46be031047de27e37366c
Signed-off-by: Edwin Kempin <ekempin@google.com>

gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/rest/change/CreateChangeIT.java

@@ -113,6 +113,8 @@ public class CreateChangeIT extends AbstractDaemonTest {
           repo.exactRef(ChangeNoteUtil.changeRefName(new Change.Id(c._number)))
               .getObjectId());
 
+      assertThat(commit.getShortMessage()).isEqualTo("Create change");
+
       PersonIdent expectedAuthor = ChangeNoteUtil.newIdent(
           accountCache.get(admin.id).getAccount(), c.created, serverIdent.get(),
           AnonymousCowardNameProvider.DEFAULT);