update_payload: Add the remaining major version 2 signature supports

This patch fixes the issues with signatures (sizes) in major version 2 and a few
minor issues with the payload and metadata sizes.

BUG=chromium:862679
TEST=manually signing the payload and running update_payload_check
TEST=unittests

Change-Id: I9b431379b0574a150474a913f1ec4a11e86288ae
Reviewed-on: https://chromium-review.googlesource.com/1363339
Commit-Ready: Amin Hassani <ahassani@chromium.org>
Tested-by: Amin Hassani <ahassani@chromium.org>
Reviewed-by: Sen Jiang <senj@chromium.org>
diff --git a/scripts/update_payload/checker_unittest.py b/scripts/update_payload/checker_unittest.py
index 98bf612..7e52233 100755
--- a/scripts/update_payload/checker_unittest.py
+++ b/scripts/update_payload/checker_unittest.py
@@ -892,7 +892,7 @@
         total_src_blocks = 16
 
     # TODO(tbrindus): add major version 2 tests.
-    payload_checker.major_version = 1
+    payload_checker.major_version = common.CHROMEOS_MAJOR_PAYLOAD_VERSION
     if op_type in (common.OpType.REPLACE, common.OpType.REPLACE_BZ):
       payload_checker.minor_version = 0
     elif op_type in (common.OpType.MOVE, common.OpType.BSDIFF):