RFR(S): 8006637 Failure to filter out native frame events on Solaris

[Staffan Larsen]

Please review the following test fix.

webrev: http://cr.openjdk.java.net/~sla/8006637/webrev.00/
bug: http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=8006637

The problem is that the test assumes that no other threads call String.intern() while the tests is running. This is normally ok, but when running with JFR there are other threads calling String.intern() in the background and the test fails. The solution is to add a thread filter to the method exit requests so that only calls to String.inter() in the main thread are reported.

Thanks,
/Staffan