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
(cherry picked from commit 7b3910a58bd0b8d9f0bd316fad5776ef0a8494ba)
Merged-In: I8601b661924abcc82956788e2f33cdb70d71f778
diff --git a/common/dynamic_partition_control_stub.cc b/common/dynamic_partition_control_stub.cc
index 1239eab..903b7ee 100644
--- a/common/dynamic_partition_control_stub.cc
+++ b/common/dynamic_partition_control_stub.cc
@@ -51,7 +51,7 @@
   return true;
 }
 
-bool DynamicPartitionControlStub::FinishUpdate() {
+bool DynamicPartitionControlStub::FinishUpdate(bool powerwash_required) {
   return true;
 }