[jdk17u-dev] RFR: 8342811: java/net/httpclient/PlainProxyConnectionTest.java failed: Unexpected connection count: 5

[Goetz Lindenmaier]

I backport this for parity with 17.0.15-oracle.

I had to resolve because "8308310:` HttpClient: Avoid logging or locking from within synchronized blocks" is not in 17.

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Commit messages:
 - Backport 59ffac84d39250623b0e6bcb871b5b3fe9c9cfe6

Changes: https://git.openjdk.org/jdk17u-dev/pull/3146/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=3146&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8342811
  Stats: 21 lines in 1 file changed: 15 ins; 0 del; 6 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/3146.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/3146/head:pull/3146

PR: https://git.openjdk.org/jdk17u-dev/pull/3146