RFR 8209821: Make JVMTI GetClassLoaderClasses not walk CLDG

[coleen.phillimore at oracle.com]

Summary: And also added function with KlassClosure to remove the hacks.

There are about 10 vmTestbase/nsk/jvmti tests that test various parts of 
this change.  Also ran mach5 tier1-7.

open webrev at http://cr.openjdk.java.net/~coleenp/8209821.01/webrev
bug link https://bugs.openjdk.java.net/browse/JDK-8209821

Thanks,
Coleen