RFR: 8348107: test/jdk/java/net/httpclient/HttpsTunnelAuthTest.java fails intermittently

[Daniel Fuchs]

The test/jdk/java/net/httpclient/HttpsTunnelAuthTest.java has been observed failing at least once. The suspicion is that it may be due to the client URI using "localhost" instead of a literal IP. 

The test has also been slightly refactored to close the created HttpClient instances after use.

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Commit messages:
 - 8348107: test/jdk/java/net/httpclient/HttpsTunnelAuthTest.java fails intermittently

Changes: https://git.openjdk.org/jdk/pull/23203/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23203&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8348107
  Stats: 19 lines in 1 file changed: 4 ins; 2 del; 13 mod
  Patch: https://git.openjdk.org/jdk/pull/23203.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23203/head:pull/23203

PR: https://git.openjdk.org/jdk/pull/23203