Reduce VABC memory usage am: e47767a5a8

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/2592048

Change-Id: Ia62066090fd5c247ea8cf53662d38f161002eba5
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>