RFR: 8342811: java/net/httpclient/PlainProxyConnectionTest.java failed: Unexpected connection count: 5 [v3]

[Volkan Yazıcı]

> This PR introduces the following changes addressing intermittent `PlainProxyConnectionTest` failures reported in [JDK-8342811](https://bugs.openjdk.org/browse/JDK-8342811):
> 
> * Increase logging verbosity to aid in troubleshooting (if the failure happens to pop up again)
> * Add salt to the used HTTP server path to decrease the chances of parallel running tests from interfering

Volkan Yazıcı has updated the pull request incrementally with one additional commit since the last revision:

  Remove references to the ticket ID

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Changes:
  - all: https://git.openjdk.org/jdk/pull/22003/files
  - new: https://git.openjdk.org/jdk/pull/22003/files/295ff767..8cec4a77

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=22003&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=22003&range=01-02

  Stats: 3 lines in 1 file changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/22003.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22003/head:pull/22003

PR: https://git.openjdk.org/jdk/pull/22003