Allow forward merge on powerwash.

If package schedules powerwash, snapshots on a Virtual A/B device
will be deleted. Tell SnapshotManager to handle this case.

Test: apply downgrade package
Test: apply package with wipe
Test: apply package then manually wipe
Bug: 152094219
Change-Id: I8601b661924abcc82956788e2f33cdb70d71f778
diff --git a/dynamic_partition_control_android.cc b/dynamic_partition_control_android.cc
index 81d0d77..09f61ad 100644
--- a/dynamic_partition_control_android.cc
+++ b/dynamic_partition_control_android.cc
@@ -624,11 +624,11 @@
   return true;
 }
 
-bool DynamicPartitionControlAndroid::FinishUpdate() {
+bool DynamicPartitionControlAndroid::FinishUpdate(bool powerwash_required) {
   if (GetVirtualAbFeatureFlag().IsEnabled() &&
       snapshot_->GetUpdateState() == UpdateState::Initiated) {
     LOG(INFO) << "Snapshot writes are done.";
-    return snapshot_->FinishedSnapshotWrites();
+    return snapshot_->FinishedSnapshotWrites(powerwash_required);
   }
   return true;
 }