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

[George Triantafillou]

Please review the following fix:

     JBS: https://bugs.openjdk.java.net/browse/JDK-8021774
     Webrev: 
http://cr.openjdk.java.net/~mseledtsov/sponsored/george.triantafillou/8021774/webrev.02/

This is a test stabilization change. The goal of this change is to 
ignore warnings with -XX:NativeMemoryTracking on Solaris and Linux in 
order to achieve a full pass of jtreg runtime tests.

Thank you,
George