RFR 8154525, java/net/ServerSocket/ThreadStop.java fails intermittently with error while cleaning up threads after test

[Felix Yang]

Hi all,

     please review following test fix.

Bug:

     https://bugs.openjdk.java.net/browse/JDK-8154525

Webrev:

     http://cr.openjdk.java.net/~xiaofeya/8154525/webrev.00/

This test has been observed to fail sometimes with "Error while cleaning 
up threads after test ", even after test complete message printed. 
Updated it to run with othervm mode.

Thanks,

Felix