invalid -affinity-cpus returns with wrong retcode

[zhangyangyu]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

./bin/tidb-server -affinity-cpus x; echo $?

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

1

3. What did you see instead (Required)

0

4. What is your TiDB version? (Required)

[zhangyangyu]

/assign @zhangyangyu

[github-actions]

Please check whether the issue should be labeled with 'affects-x.y' or 'fixes-x.y.z', and then remove 'needs-more-info' label.