Make test data generation reproducible am: 7c7e7faf56 am: b2d600a55e

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/2774950

Change-Id: I8b77e2c715aaf6eee85759f23406e00228c8d5b2
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>