RFR: a couple fixes to C2 verification code for CAS

[Roman Kennke]

Good! Thanks!
Roman


> http://cr.openjdk.java.net/~roland/shenandoah/cas-verif-fixes/webrev.00/
> 
> - Verification code doesn't trigger for CAS when compressed oops are
>   enabled
> - Verification code is broken for CAS with traversal
> 
> Roland.
>