Changing `Util.shutdown()` to hide **all** showing Windows and then call `Platform.exit()`. This simplifies the tests and ensures a clean shutdown.
------------- Commit messages: - copy - 8325566: [TestBug] Util.shutdown() to hide ALL the scenes Changes: https://git.openjdk.org/jfx/pull/1407/files Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1407&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8325566 Stats: 124 lines in 59 files changed: 1 ins; 6 del; 117 mod Patch: https://git.openjdk.org/jfx/pull/1407.diff Fetch: git fetch https://git.openjdk.org/jfx.git pull/1407/head:pull/1407 PR: https://git.openjdk.org/jfx/pull/1407
