ccl/sqlproxyccl: TestFrontendAdmitWithClientSSLDisableAndCustomParam failed

ccl/sqlproxyccl.TestFrontendAdmitWithClientSSLDisableAndCustomParam [failed](https://mesolite.cluster.engflow.com/invocations/default/96518768-5798-46c8-b5ad-b1f76de37069?testReportRun=2&testReportShard=3&testReportAttempt=1#targets-Ly9wa2cvY2NsL3NxbHByb3h5Y2NsOnNxbHByb3h5Y2NsX3Rlc3Q=) on release-26.1 @ [e731910a1ca56e711b15b2c9348f218a9f160d3a](https://github.com/cockroachdb/cockroach/commits/e731910a1ca56e711b15b2c9348f218a9f160d3a):

```
=== RUN TestFrontendAdmitWithClientSSLDisableAndCustomParam
frontend_admitter_test.go:80:
Error Trace: pkg/ccl/sqlproxyccl/frontend_admitter_test.go:80
Error: Received unexpected error:
codeClientReadFailed: while receiving startup message: read pipe: i/o timeout
(1) codeClientReadFailed
Wraps: (2) attached stack trace
-- stack trace:
| github.com/cockroachdb/cockroach/pkg/ccl/sqlproxyccl.init.func7
| pkg/ccl/sqlproxyccl/frontend_admitter.go:68
| github.com/cockroachdb/cockroach/pkg/ccl/sqlproxyccl.TestFrontendAdmitWithClientSSLDisableAndCustomParam
| pkg/ccl/sqlproxyccl/frontend_admitter_test.go:79
| testing.tRunner
| GOROOT/src/testing/testing.go:1934
| runtime.goexit
| src/runtime/asm_amd64.s:1693
Wraps: (3) while receiving startup message
Wraps: (4) read pipe
Wraps: (5) i/o timeout
Error types: (1) *sqlproxyccl.errWithCode (2) *withstack.withStack (3) *errutil.withPrefix (4) *net.OpError (5) *poll.DeadlineExceededError
Test: TestFrontendAdmitWithClientSSLDisableAndCustomParam
--- FAIL: TestFrontendAdmitWithClientSSLDisableAndCustomParam (3.00s)
```

Parameters:
- attempt=1
- race=true
- run=2
- shard=3
Help

See also: [How To Investigate a Go Test Failure \(internal\)](https://cockroachlabs.atlassian.net/l/c/HgfXfJgM)

/cc @cockroachdb/sqlproxy-prs

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Jira issue: CRDB-61922