[14] RFR 8237038: Shenandoah: Reduce thread pool size in TestEvilSyncBug.java test

[Zhengyu Gu]

Please review this small patch to reduce thread pool size in 
TestEvilSyncBug.java test.

I have observed problems with the test on many core system, including 
crashes on arm server with 48 cores when running 4 concurrent test jobs.


Bug: https://bugs.openjdk.java.net/browse/JDK-8237038
Webrev: http://cr.openjdk.java.net/~zgu/JDK-8237038/webrev.00/


Test:
   hotspot_gc_shenandoah (fastdebug and release) with 4 concurrent test 
jobs on 48 cores arm machine.

Thanks,

-Zhengyu