Map all partitions before calling FinishUpdate for VAB as well am: b88b4ba12a am: ed342382fd

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/3472588

Change-Id: Ia11880d57b5d77b048922f621abb049a2372fb01
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>