RFR: 8376308: java/net/httpclient/CancelRequestTest.java fails intermittently with "Expected CancellationException not received" [v2]

[Daniel Fuchs]

> When using async mode, and if the "wrong" test/client thread gets suspended at the wrong time there's a small time window in which the server might be able to send its reply before the request is cancelled.
> This can be avoided by having the server handler wait on a semaphore until the cancellation exception has been propagated to the caller on the client side.

Daniel Fuchs has updated the pull request incrementally with one additional commit since the last revision:

  Review feedback

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Changes:
  - all: https://git.openjdk.org/jdk/pull/29415/files
  - new: https://git.openjdk.org/jdk/pull/29415/files/51dd06eb..4fa0b27a

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=29415&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=29415&range=00-01

  Stats: 39 lines in 1 file changed: 4 ins; 9 del; 26 mod
  Patch: https://git.openjdk.org/jdk/pull/29415.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29415/head:pull/29415

PR: https://git.openjdk.org/jdk/pull/29415