RFR: 8247266: Speed up test\jdk\jdk\jfr\event\gc\detailed\TestZUncommitEvent.java

[Erik Gahlin]

Hi,

Could I have a review of a fix thats speeds up a test

Webrev:
http://cr.openjdk.java.net/~egahlin/8247266/

Bug:
https://bugs.openjdk.java.net/browse/JDK-8247266

Testing: 
Ran the test 100 times on Mac, Linux and Windows

Thanks
Erik