Propagate the merge failure code to SnapshotMergeStats.

Bug: 185290850
Test: manual test
Change-Id: I094c705a5a275e289eddb8f42e68e08f56975c83
diff --git a/aosp/cleanup_previous_update_action.cc b/aosp/cleanup_previous_update_action.cc
index 68954f6..a902eaf 100644
--- a/aosp/cleanup_previous_update_action.cc
+++ b/aosp/cleanup_previous_update_action.cc
@@ -324,6 +324,7 @@
 
     case UpdateState::MergeFailed: {
       LOG(ERROR) << "Merge failed. Device may be corrupted.";
+      merge_stats_->set_merge_failure_code(snapshot_->ReadMergeFailureCode());
       processor_->ActionComplete(this, ErrorCode::kDeviceCorrupted);
       return;
     }