[jdk21u-dev] RFR: 8352706: httpclient HeadTest does not run on HTTP2

[Goetz Lindenmaier]

I backport this for parity with 21.0.8-oracle.

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Commit messages:
 - Backport e32a0c90feb231d791e6c17e6360f629189cab8b

Changes: https://git.openjdk.org/jdk21u-dev/pull/1709/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1709&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8352706
  Stats: 23 lines in 1 file changed: 7 ins; 11 del; 5 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/1709.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/1709/head:pull/1709

PR: https://git.openjdk.org/jdk21u-dev/pull/1709