RFR: 8326568: jdk/test/com/sun/net/httpserver/bugs/B6431193.java should use try-with-resource and try-finally

[Darragh Clarke]

Currently this test occasionally doesn't cleanup between runs, sometimes not stopping the server or leaving Streams open

Changes:
- Use try-with-resources to ensure streams close.
- Use try-finally to make sure the server stops before the test exits.

I ran tiers 1-3 and ran this specific test on repeat and everything seems stable after the changes

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Commit messages:
 - use try-finally and try-with-resources as well as slight cleanup

Changes: https://git.openjdk.org/jdk/pull/18514/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18514&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8326568
  Stats: 34 lines in 1 file changed: 3 ins; 10 del; 21 mod
  Patch: https://git.openjdk.org/jdk/pull/18514.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18514/head:pull/18514

PR: https://git.openjdk.org/jdk/pull/18514