RFR: 8350924: javax/swing/JMenu/4213634/bug4213634.java fails

[Prasanta Sadhukhan]

Test fails in ubuntu OCI system..Made it more robust my adding waitForIdle/delay before commencing test..
OCI system is ok with the fix.

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

Commit messages:
 - 8350924: javax/swing/JMenu/4213634/bug4213634.java fails

Changes: https://git.openjdk.org/jdk/pull/23837/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23837&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8350924
  Stats: 40 lines in 1 file changed: 6 ins; 14 del; 20 mod
  Patch: https://git.openjdk.org/jdk/pull/23837.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23837/head:pull/23837

PR: https://git.openjdk.org/jdk/pull/23837