RFR: 8373807: test/jdk/java/net/httpclient/websocket/DummyWebSocketServer.java getURI() uses "localhost"

[Daniel Fuchs]

The WebSockteTest was observed failing in timeout once, waiting for the completable future returned by `WebSocketBuilder::build` to complete. The suspicion is that it may have been caused by the request being misdirected due to the use of "localhost" in the URI. 

This trivial fix ensures that the DumyWebSocketServer::getURI returns a URI with a literal IP address instead of relying on "localhost".

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Commit messages:
 - 8373807: test/jdk/java/net/httpclient/websocket/DummyWebSocketServer.java getURI() uses "localhost"

Changes: https://git.openjdk.org/jdk/pull/28864/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28864&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8373807
  Stats: 8 lines in 1 file changed: 7 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/28864.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28864/head:pull/28864

PR: https://git.openjdk.org/jdk/pull/28864