RFR: 8295991: java/net/httpclient/CancelRequestTest.java fails intermittently [v2]

[Daniel Fuchs]

> The CancelRequestTest test has been observed failing (once). It was recently updated to verify that subscribers would be correctly unregistered after the request was cancelled. However, the timeout used to wait for that to happen was optimistically too short: the test code that cancels the request is by design racy, so it's not guaranteed that the subscriber will be unregistered before the completable future is cancelled, it might get unregistered asynchronously shortly after.
> Increasing the timeout to wait for that to happen from 1ms to 100ms fixes the test issue.

Daniel Fuchs has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:

 - Merge branch 'master' into cancel-request-test-8295991
 - Narrow down tracking to the client used by the test. Increase timeout.
 - 8295991

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Changes:
  - all: https://git.openjdk.org/jdk/pull/10931/files
  - new: https://git.openjdk.org/jdk/pull/10931/files/9631fbe2..a7d400b0

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10931&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10931&range=00-01

  Stats: 3859 lines in 203 files changed: 2456 ins; 592 del; 811 mod
  Patch: https://git.openjdk.org/jdk/pull/10931.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10931/head:pull/10931

PR: https://git.openjdk.org/jdk/pull/10931