<Swing Dev> RFR: 8233641: [TESTBUG] JMenuItem test bug4171437.java fails on macos

[Prasanta Sadhukhan]

Please review a test fix for a test issue seen to be failing on mach5 macos systems due to timing issue.
Modified the test to modify setAutoDelay() time, added delay() after frame is made visible and moved the frame to centre of screen.
Mach5 job has been run for several iterations in all platforms. Link in JBS.

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

Commit messages:
 - 8233641: [TESTBUG] JMenuItem test bug4171437.java fails on macos

Changes: https://git.openjdk.java.net/jdk/pull/922/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=922&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8233641
  Stats: 8 lines in 2 files changed: 4 ins; 4 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/922.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/922/head:pull/922

PR: https://git.openjdk.java.net/jdk/pull/922