old value feature can't be turned off if changefeed has enabled it

[amyangfei]

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.

   1. create two changefeed with `enable-old-value=true`, and replicate with a same table
   2. pause one of the changefeed (changefeed-1)
   3. update changefeed-1, set `enable old value = false`
   4. resume changefeed-1, the output result from changefeed-1 still contain old-value column
   

2. What did you expect to see?

   old-value feature can be turned off

3. What did you see instead?

   old-value feature can't be turned off

4. Versions of the cluster

   • Upstream TiDB cluster version (execute SELECT tidb_version(); in a MySQL client):

     v4.0.9
     

   • TiCDC version (execute cdc version):

     v4.0.9
     

5. Others

• We need to confirm when multiple changefeeds exist, whether changefeed with old-value enabled will affect changefeed with old-value turned off.

there is another way to reproduce the error:

    1. create a changefeed to listen table1 with `enable-old-value=true`
    2. create another changefeed to listen the same table1 with `enable-old-value=false`

we can see that all of changefeed will output the row changed event with old value

[amyangfei]

TiKV fix in tikv/tikv#9515