RFR(XSS): 8032763: Remove use of sun.misc.Ref from hprof parser in testlibrary

[Yekaterina Kantserova]

Hi,

Could I please have a review of this very small fix.

bug: https://bugs.openjdk.java.net/browse/JDK-8032763
webrev: http://cr.openjdk.java.net/~ykantser/8032763/webrev.00

Thanks,
Katja