RFR: 8237221 [macos] java/awt/MenuBar/SeparatorsNavigation/SeparatorsNavigation.java fails

[Alexander Zuev]

Hello!

  Please review fix for the jdk/client.
Bug: https://bugs.openjdk.java.net/browse/JDK-8237221
Fix: http://cr.openjdk.java.net/~kizune/8237221/webrev 
<http://cr.openjdk.java.net/~kizune/8237221/webrev/>

I excluded Mac OS from the test targets and did some code cleanup.

/Alex