<Swing Dev> RFR: 8196092: javax/swing/JComboBox/8032878/bug8032878.java fails

[Prasanta Sadhukhan]

Test was failing if JComboBox tests was run in group in nightly mach5 testing.
Modified test to remove dependancy from Util class, added delay before frame show and move frame to centre of screen.
Resultant modified test ran fine in JComboBox group and also in standalone, several iterations of which are ran in mach5. Link in JBS.

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Commit messages:
 - 8196092: javax/swing/JComboBox/8032878/bug8032878.java fails

Changes: https://git.openjdk.java.net/jdk/pull/1762/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1762&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8196092
  Stats: 21 lines in 2 files changed: 11 ins; 4 del; 6 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1762.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1762/head:pull/1762

PR: https://git.openjdk.java.net/jdk/pull/1762