the count of stats_meta is zero when restore if backup has no checksum

[Leavrth]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

1. backup with --checksum=false
2. snapshot restore

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

the count of stats_meta is larger than 0.

3. What did you see instead (Required)

the count of stats_meta is 0.

4. What is your TiDB version? (Required)

master