multi: add reset closure to kvdb.Update

Similarly as with kvdb.View this commits adds a reset closure to the
kvdb.Update call in order to be able to reset external state if the
underlying db backend needs to retry the transaction.

channeldb/migration_01_to_11/db.go

@@ -152,7 +152,7 @@ func createChannelDB(dbPath string) error {
 			DbVersionNumber: 0,
 		}
 		return putMeta(meta, tx)
-	})
+	}, func() {})
 	if err != nil {
 		return fmt.Errorf("unable to create new channeldb")
 	}