Improve error message when hitting checksum mismatch am: 88d1069f50 am: fbc46a7bbb am: 3d6f3cc00d

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/1355944

Change-Id: Ied6ec2c3022156de19e964156aa9bbec39d8d147