RFR 8029178: Parallel class loading test anonymous-simple gets SIGSEGV in Metaspace:,:contains

[Coleen Phillmore]

Summary: Metaspace::contains cannot look at purged metaspaces while CMS 
concurrently deallocates them.

Removed 2 calls to is_metaspace_object where the object may be in a 
deallocated metaspace.  Removed walking virtual space lists for 
determining contains because the virtual space list can change 
concurrently with the walk.   CLDG::contains is slower but no slowdowns 
with testing were observed.

Tested by SQE testbase tests, jtreg tests.   Functional testing by 
parallel class loading tests and nsk/coverage/arguments/arguments008 
(ie. calls Method::is_valid_method)

open webrev at http://cr.openjdk.java.net/~coleenp/8029178/
bug link https://bugs.openjdk.java.net/browse/JDK-8029178

Thanks,
Coleen