RFR: JDK-8222323: ChildAlwaysOnTopTest.java fails with "RuntimeException: Failed to unset alwaysOnTop"

[Harshitha Onkar]

This test case tests the functionality of `setAlwaysOnTop`. 
Documentation on `setAlwaysOnTop`: [Link](https://docs.oracle.com/en/java/javase/17/docs/api/java.desktop/java/awt/Window.html#setAlwaysOnTop(boolean))

The following test case was seen to fail on windows and linux platforms. With the proposed fix, the test case works on all platforms.

The test case tests `alwaysOnTop` for the following three cases:

1.	JDialog with no parent/owner
2.	JDialog with JFrame as owner
3.	JDialog with another JDialog as owner

Each of the three cases mentioned above is tested under 3 scenarios:
![Screen Shot 2022-05-02 at 2 02 30 PM](https://user-images.githubusercontent.com/95945681/166327299-0fb5ce14-478d-4dee-a03a-1009a8e17047.png)

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Commit messages:
 - test case changes for alwaysOnTop

Changes: https://git.openjdk.java.net/jdk/pull/8509/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8509&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8222323
  Stats: 203 lines in 2 files changed: 106 ins; 9 del; 88 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8509.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8509/head:pull/8509

PR: https://git.openjdk.java.net/jdk/pull/8509