unstable test TestCheckCN

[hawkingrei]

Bug Report

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1. Minimal reproduce step (Required)

[2022-08-03T13:19:31.445Z]     security_test.go:141: 

[2022-08-03T13:19:31.445Z]         	Error Trace:	security_test.go:141

[2022-08-03T13:19:31.445Z]         	Error:      	Expect "Get "https://127.0.0.1:9292/": write tcp 127.0.0.1:60364->127.0.0.1:9292: write: connection reset by peer" to match ".*tls: bad certificate"

[2022-08-03T13:19:31.445Z]         	Test:       	TestCheckCN

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

3. What did you see instead (Required)

4. What is your TiDB version? (Required)