Fix download progress offset error am: 5440fe3cfe am: 5b5dab7ec2

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/2870744

Change-Id: Ie1b95bfd688960383bbe76bf9d3c191276f168ac
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>