RFR (S) 8199007: ClassLoaderDataGraph::unload_list_contains() is wrong

[coleen.phillimore at oracle.com]

Summary: The function isn't needed any longer.

I believe the function existed from an earlier day when 
Metaspace::contains walked the CLDG, so you needed a function to walk 
the unloaded list as well.

Tested with Per's GC test suite and mach5 tier1-5 (until it failed in 
infra for some platforms), and my own local testing like:

jtreg -exclude:open/test/hotspot/jtreg/ProblemList.txt 
open/test/hotspot/jtreg:hotspot_all_no_apps

(and the closed jtreg tests too).

open webrev at http://cr.openjdk.java.net/~coleenp/8199007.01/webrev
bug link https://bugs.openjdk.java.net/browse/JDK-8199007

Thanks,
Coleen