RFR: 8288707: javax/swing/JToolBar/4529206/bug4529206.java: setFloating does not work correctly

[Prasanta Sadhukhan]

Test was failing intermittently around 1 or 2 out of 30 runs. 
Fixed by adding stability code, wait for a sec after frame is visible, set frame to center.
Modified test has run at least 50 times in all platforms and 100 times in linux (where it is seen intermittently) without any issue.

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Commit messages:
 - Fix
 - 8288707: javax/swing/JToolBar/4529206/bug4529206.java: setFloating does not work correctly

Changes: https://git.openjdk.org/jdk/pull/9269/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9269&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8288707
  Stats: 63 lines in 1 file changed: 34 ins; 9 del; 20 mod
  Patch: https://git.openjdk.org/jdk/pull/9269.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9269/head:pull/9269

PR: https://git.openjdk.org/jdk/pull/9269