RFR: 8079267: [TEST_BUG] Test java/awt/Frame/MiscUndecorated/RepaintTest.java fails

[Alexander Zvegintsev]

This test does not fail on Windows and does fail on Linux. 

After de-iconification we expect to see the button focused:
![image](https://user-images.githubusercontent.com/77687766/139171852-54413dba-d58a-46d4-ab83-59d93868e287.png)

Actual look:
![image](https://user-images.githubusercontent.com/77687766/139171775-80e64e58-c49d-489a-8fe0-fb0640fc3be9.png)

Button loses focus on `frame.to Front()` call, after its removal test passes. 
There is an [open issue](https://bugs.openjdk.java.net/browse/JDK-7156130) for 
this.


Some cleanup was also made. Testing is green for all platforms.


I am unable to reproduce [8266244 / 
macosx-aarch64](https://bugs.openjdk.java.net/browse/JDK-8266244), however it 
is not removed from the problem list due to its intermittent nature which needs 
more time to investigate.

-------------

Commit messages:
 - linux fix
 - initial

Changes: https://git.openjdk.java.net/jdk/pull/6157/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6157&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8079267
  Stats: 47 lines in 2 files changed: 14 ins; 24 del; 9 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6157.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6157/head:pull/6157

PR: https://git.openjdk.java.net/jdk/pull/6157