Count result may be wrong after a lot of insert and delete

[lidezhu]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

Repeated do a lot of insert rows and delete alls.
Keep select count after after every operation.

2. What did you expect to see? (Required)

Count result is right.

3. What did you see instead (Required)

Count result is wrong. The number of rows in TiFlash is larger than that in TiKV

4. What is your TiFlash version? (Required)