RFR: 8308336: Test java/net/HttpURLConnection/HttpURLConnectionExpectContinueTest.java failed: java.net.BindException: Address already in use

[Darragh Clarke]

`HttpURLConnectionExpectContinueTest` was throwing an error due to port being hardcoded, updated test to let the system decide which port to use.

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Commit messages:
 - change test to use ephemeral port

Changes: https://git.openjdk.org/jdk/pull/14177/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14177&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8308336
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/14177.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14177/head:pull/14177

PR: https://git.openjdk.org/jdk/pull/14177