Skip FEC reads for partial updates am: 212b053645 am: 1a78774dcd

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/3356640

Change-Id: Ia48e88d167fbb2610810bea6b871df3f86205290
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>