[9] Review request for 8164473: [TEST_BUG] Series of modal/focus tests fail always on Unity

[Semyon Sadetsky]

Hello,

Please review fix for JDK9:
bug:https://bugs.openjdk.java.net/browse/JDK-8164473

webrev: http://cr.openjdk.java.net/~ssadetsky/8164473/webrev.00/

Stability of ModalExcludedWindowClickTest was improved. The rest tests 
mentioned in the bug are stably pass after JDK-8161910 is fixed.

Tested on dual-screen Ubuntu 16.04.

--Semyon