Do not include signature dummy operation in major version 2.

It only exists for compatibility reason, for major version 2, there's no
point to add this any more.

Bug: None
TEST=Applied the new payload to a device.

Change-Id: I5803ab755415a1ba3d7460d82956bfe6e9fd4547
diff --git a/payload_generator/payload_file.cc b/payload_generator/payload_file.cc
index 17baf46..ae4896a 100644
--- a/payload_generator/payload_file.cc
+++ b/payload_generator/payload_file.cc
@@ -166,8 +166,9 @@
     TEST_AND_RETURN_FALSE(
         PayloadSigner::SignatureBlobLength(vector<string>(1, private_key_path),
                                            &signature_blob_length));
-    PayloadSigner::AddSignatureOp(next_blob_offset, signature_blob_length,
-                                  &manifest_);
+    PayloadSigner::AddSignatureToManifest(
+        next_blob_offset, signature_blob_length,
+        major_version_ == kChromeOSMajorPayloadVersion, &manifest_);
   }
 
   // Serialize protobuf