Stabilize backup request policy test cleanup

[wasphin]

What problem does this PR solve?

Issue Number: N/A

Problem Summary:

The backup request policy test used a fatal assertion while waiting for short
connections to close. On a slow CI runner, the assertion could return from the
helper before StopAndJoin(), leaving the acceptor active while later parameter
combinations continued to run.

What is changed and the side effects?

Changed:

Record a connection-close timeout, stop and join the acceptor, and then report
the failure. Allow up to one second for asynchronous short-connection cleanup
so the test does not enforce a 100 ms timing assumption unrelated to backup
request policy behavior.

Side effects:

• Performance effects: Test-only change; no production performance impact.

• Breaking backward compatibility: No.

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Check List:

• Please make sure your changes are compilable.
• When providing us with a new feature, it is best to add related tests.
• Please follow Contributor Covenant Code of Conduct.

[Copilot]

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Copilot review overview

Review effort: Lite
Findings: 1

Open (1)

• The 1000000L timeout is a magic number without context/comment. Consider replacing it with a… · New

What changed in this PR

This PR stabilizes the TestBackupRequestPolicy unit test by avoiding a fatal assertion while waiting for short connections to close, ensuring the acceptor is always stopped/joined before reporting a failure (especially on slow CI runners).

Changes:

• Replace a fatal 100ms timeout assertion with a non-fatal timeout flag and post-cleanup expectation.
• Increase the wait time for short-connection cleanup to 1 second to reduce CI flakiness.
• Ensure StopAndJoin() runs even when the close-wait times out by breaking out of the parameter loop and reporting afterward.

File	Description
test/​brpc_channel_unittest.cpp	Makes short-connection cleanup waiting non-fatal and increases timeout to reduce test flakiness while preserving cleanup (StopAndJoin()).

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[wasphin]

A flaky unit-test is fixed by #3567

[Copilot]

Copilot review overview

🟢 Approval recommended

No unresolved blocking issues were identified.

Review effort: Lite
Findings: None

Resolved since last review (1)

• The 1000000L timeout is a magic number without context/comment. Consider replacing it with a…

[chenBright]

LGTM