[FLINK-35274][cdc-connector][db2] Fix occasional failure issue with Flink CDC Db2 UT

flink-cdc-connect/flink-cdc-source-connectors/flink-connector-db2-cdc/src/main/java/io/debezium/connector/db2/Db2Connection.java

@@ -323,7 +323,8 @@ public class Db2Connection extends JdbcConnection {
                          */
                         changeTables.add(
                                 new Db2ChangeTable(
-                                        new TableId("", rs.getString(1), rs.getString(2)),
+                                        new TableId(
+                                                realDatabaseName, rs.getString(1), rs.getString(2)),
                                         rs.getString(4),
                                         rs.getInt(9),
                                         Lsn.valueOf(rs.getBytes(5)),