Check for metadata hash if specified am: abb082f499

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/2568976

Change-Id: Ib1de68b3e899a4a622605319f76c9722bd0099b8
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>