[jdk11u-dev] RFR: 8291637: HttpClient default keep alive timeout not followed if server sends invalid value

[Goetz Lindenmaier]

I backport this for parity with 11.0.20-oracle.

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Commit messages:
 - Backport b17a745d7f55941f02b0bdde83866aa5d32cce07

Changes: https://git.openjdk.org/jdk11u-dev/pull/1819/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=1819&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8291637
  Stats: 147 lines in 2 files changed: 147 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/1819.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/1819/head:pull/1819

PR: https://git.openjdk.org/jdk11u-dev/pull/1819