sync-diff will not report error when upstream has table but downstream doesn't

[lance6716]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. What did you do?
   If possible, provide a recipe for reproducing the error.

upstream has all_mode.t2 and t1, downstream has all_mode.t2

2. What did you expect to see?

error: table all_mode.t1 does not exists in downstream

3. What did you see instead?

$ bin/sync_diff_inspector --config ~/Projects/ticdc/dm/tests/all_mode/conf/diff_config.toml
A total of 1 tables need to be compared

Comparing the table structure of ``all_mode`.`t2`` ... equivalent
Comparing the table data of ``all_mode`.`t2`` ... equivalent
_____________________________________________________________________________
Progress [============================================================>] 100% 0/Progress [============================================================>] 100% 0/0
A total of 1 table have been compared and all are equal.
You can view the comparision details through '/tmp/ticdc_dm_test/output/sync_diff.log'

4. What version of TiDB are you using (tidb-server -V or run select tidb_version(); on TiDB)?

5. which tool are you using?

6. what versionof tool are you using (pump -V or tidb-lightning -V or syncer -V)?

[lance6716]

need revert pingcap/tiflow#3413 after this is fix