RFR: 8373946: Synth ProgressBarUI implementation confuses background painting with border painting

[Prasanta Sadhukhan]

[JDK-8224261](https://bugs.openjdk.org/browse/JDK-8224261) fix controls background painting by checking if border is painted or not. This is wrong as background should always be painted else background will not be painted if border is not there
JProgressBar.setBorderPainted spec says " Some look and feels might not implement painted borders; they will ignore this property." so not painting border is ok but not painting background is an issue

The JDK-8224261 is hereby backed out

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Commit messages:
 - jcheck
 - 8373946: Synth ProgressBarUI implementation confuses background painting with border painting

Changes: https://git.openjdk.org/jdk/pull/28885/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28885&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8373946
  Stats: 219 lines in 3 files changed: 105 ins; 110 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/28885.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28885/head:pull/28885

PR: https://git.openjdk.org/jdk/pull/28885