unnecessary cgroup logs printed when running cdc cli in container env

[fubinzh]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

1. run cdc in container env
2. run /cdc version or /cdc cli changefeed list command.

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

/cdc cli only output inforamtion that is required.

3. What did you see instead (Required)

cdc cli output some uncennsary information related to cgroup, this might confuse users. due to

tidb/pkg/util/cgroup/cgroup_cpu_linux.go

Line 96 in 224ae15

log.Info(fmt.Sprintf("TiDB runs in a container, mount info: %s", line))

4. What is your TiDB version? (Required)

master