Save finalized checkpoint before migrate to cold (#7055)

* Save finalized checkpoint before migrate to cold
* Save finalized checkpoint before migrate to cold
* Merge branch 'master' into save-checkpoint-first

beacon-chain/blockchain/process_block_helpers.go

@@ -226,6 +226,11 @@ func (s *Service) updateFinalized(ctx context.Context, cp *ethpb.Checkpoint) err
 		return err
 	}
 	s.clearInitSyncBlocks()
+	s.attPool.ClearSeenAtts()
+
+	if err := s.beaconDB.SaveFinalizedCheckpoint(ctx, cp); err != nil {
+		return err
+	}
 
 	s.prevFinalizedCheckpt = s.finalizedCheckpt
 	s.finalizedCheckpt = cp
@@ -235,9 +240,7 @@ func (s *Service) updateFinalized(ctx context.Context, cp *ethpb.Checkpoint) err
 		return errors.Wrap(err, "could not migrate to cold")
 	}
 
-	s.attPool.ClearSeenAtts()
-
-	return s.beaconDB.SaveFinalizedCheckpoint(ctx, cp)
+	return nil
 }
 
 // ancestor returns the block root of an ancestry block from the input block root.