RFR(XS): JDK-8021774: [TESTBUG] Tests failed because of a warning in its output

[Mikhailo Seledtsov]

Please review this small change to the JVM RT test.
I am posting this web rev on behalf of our new JVM Runtime SQE team 
member, George Triantafillou.

Please note, this change is part of the test stabilization effort, 
therefore it could still be checked-in to the JDK-8.

     JBS: https://bugs.openjdk.java.net/browse/JDK-8021774
     Webrev: 
http://cr.openjdk.java.net/~mseledtsov/sponsored/george.triantafillou/8021774/webrev.00/