Read boot image version from ro.bootimage.build.date.utc am: 70ba92e414 am: 394348f4e2 am: e8c848b5cc

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/1434717

Change-Id: I1d77b4d1de7d4024700c16364d7d03ef9549402b