Reset slot switch before deleting snapshots am: f92fe255d2

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/2510838

Change-Id: I1bcbff6683d62d192127662c4289a2c47cec48b6
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>