Fix cow size estimation of --vabc-none am: bfa10418a2 am: b9d8d7edde am: 36dc0e3eaf

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/2494986

Change-Id: I966822989658c07d7bd5f263242f28f4761a06e0
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>