DynamicPartitionControl: only create snapshot when snapshot_enabled

Do not create snapshot when applying downgrade
to non-Virtual-A/B packages and secondary OTAs.

Test: apply downgrade OTA on Virtual A/B devices

Bug: 138733621 (secondary OTA)
Fixes: 138258570 (downgrades)

Change-Id: I13318f57613d6bd60a5b7e81ebb3e35b3c225a0c
diff --git a/dynamic_partition_control_android_unittest.cc b/dynamic_partition_control_android_unittest.cc
index 552774e..e8ef1f9 100644
--- a/dynamic_partition_control_android_unittest.cc
+++ b/dynamic_partition_control_android_unittest.cc
@@ -112,7 +112,7 @@
   }
   bool PreparePartitionsForUpdate(const PartitionSizes& partition_sizes) {
     return dynamicControl().PreparePartitionsForUpdate(
-        source(), target(), PartitionSizesToManifest(partition_sizes));
+        source(), target(), PartitionSizesToManifest(partition_sizes), true);
   }
   void SetSlots(const TestParam& slots) { slots_ = slots; }