no need to start domain for br log operation

[Leavrth]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

1. ./br log start/stop/resume...

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

1. less memory used

3. What did you see instead (Required)

2. oom

4. What is your TiDB version? (Required)

v6.5 v7.1 v7.5 master