Reland: Map all partitions before calling FinishUpdate for VAB as well am: 67b4378f2f am: 1034794207

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/3487611

Change-Id: Ifa922ccf232a5607a13c30940e6d080a72fd8d01
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>