fix: wrap CountDownLatch.await() in assertTrue() in tests

[zhang-arvin]

Purpose

Wrap CountDownLatch.await(timeout, unit) calls in assertTrue() to prevent silent test timeouts. When the boolean return value of await() is ignored, a timeout causes the test to silently pass instead of failing.

Changes

• PostJoinCursorTest.java: wrap countDownLatch.await(1, TimeUnit.SECONDS) in assertTrue()
• CoordinatorSegmentMetadataCacheTest.java: wrap latch.await(1, TimeUnit.SECONDS) in Assert.assertTrue()
• ServerManagerTest.java: wrap 4 occurrences of factory.notifyLatch.await(1000, TimeUnit.MILLISECONDS) in Assert.assertTrue()
• JettyTest.java: wrap latch.await(5, TimeUnit.SECONDS) in Assert.assertTrue()

Closes #9285

[FrankChen021]

Severity	Findings
P0	0
P1	1
P2	0
P3	0
Total	1

Reviewed 4 of 4 changed files.

The review found one test-thread lifecycle issue that can hang the JVM after a timeout.

---

This is an automated review by Codex GPT-5.6-Luna(max)

[FrankChen021]

[P1] Timeout assertion can skip interrupt cleanup

If await returns false, the assertion throws before joinCursorThread.interrupt(). The intentionally infinite, non-daemon test thread can then continue indefinitely and hang the test JVM. Move interruption and joining into cleanup that runs before or alongside the assertion.