Rename revert message on original change

Michael Beardsworth:
> "This patchset was reverted in change: <changeId>" message is a bit
> confusing.  I'd rather have it read something more like
> "A change to revert this patchset was created: see <changeId>" so it's
> more clear that the revert hasn't been submitted.

After discussion we settle for "Created a revert of this change as %s",
because a) you can only revert the latest revision, so it's on a change
actually targeting the change rather than a particular revision and b)
it's shorter than what Michael proposed.

Change-Id: I91d3c1cb694da208f15eefbf17c139e2150a3044
Signed-off-by: Stefan Beller <sbeller@google.com>

gerrit-server/src/main/java/com/google/gerrit/server/change/Revert.java

@@ -249,10 +249,7 @@ public class Revert implements RestModifyView<ChangeResource, RevertInput>,
               ChangeUtil.messageUUID(db.get())),
           ctx.getUser().getAccountId(), ctx.getWhen(), patchSetId);
       StringBuilder msgBuf = new StringBuilder();
-      msgBuf.append("Patch Set ").append(patchSetId.get())
-          .append(": Reverted");
-      msgBuf.append("\n\n");
-      msgBuf.append("This patchset was reverted in change: ")
+      msgBuf.append("Created a revert of this change as ")
           .append("I").append(computedChangeId.name());
       changeMessage.setMessage(msgBuf.toString());
       cmUtil.addChangeMessage(ctx.getDb(), ctx.getUpdate(patchSetId),