Request for review: 7006471: fix for 6988439 crashes when pending list lock is null

[coleen phillimore]

Summary: missing null check in owns_pending_list_lock() because this can 
be called before pending_list_lock is initialized.

Tested with -XX:CompileThreshold=10 a bunch of mixed tests plus the 
failing test case.

open webrev at http://cr.openjdk.java.net/~coleenp/7006471/
bug link at http://bugs.sun.com/view_bug.do?bug_id=7006471

Thanks,
Coleen