Halve test erofs image size am: 6fb5303589 am: 1a9bea81ff

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/2234809

Change-Id: Ibae8c6b3a93d7368392d0fe03a219a59d39b34f2
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>