[jdk17u-dev] RFR: 8348107: test/jdk/java/net/httpclient/HttpsTunnelAuthTest.java fails intermittently

[Goetz Lindenmaier]

I backport this for parity with 17.0.16-oracle.

HttpClient does not implement AutoClosable in 17, so try-with-resources can not be used here.
This part of the fix is only cleanup, so we can get along without it.
I tried to keep the formatting of the code as close to 21 as possible.

https://bugs.openjdk.org/browse/JDK-8267140 Support closing the HttpClient by making it auto-closable 
came only in 21.

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Commit messages:
 - Fix build
 - Backport 5c4a387b7e5643815542dd6938e8e1dbb817ad90

Changes: https://git.openjdk.org/jdk17u-dev/pull/3372/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=3372&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8348107
  Stats: 21 lines in 1 file changed: 6 ins; 2 del; 13 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/3372.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/3372/head:pull/3372

PR: https://git.openjdk.org/jdk17u-dev/pull/3372