txn: the activation does not work as expected for some cases

[cfzjywxk]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

As @jackysp mentioned #22875 (comment).

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

The transaction should be activiated at the beginning of retry.

3. What did you see instead (Required)

It did not.

4. What is your TiDB version? (Required)

master branch 4b90ef4.

[cfzjywxk]

As the influence of this issue is not that big, change the severity to minor, it could be solved in the progress of the refactor task #22901.