RFR(S): 8228631: Fix inconsistent OopStorage::Block owner usage

[Per Liden]

Looks good!

/Per

On 7/26/19 1:41 AM, Kim Barrett wrote:
> Please review this cleanup of the use of the _owner member of
> OopStorage blocks.  It's now just the intptr_t address of the owning
> storage object, and no longer sometimes used as the actual owning
> object.
> 
> CR:
> https://bugs.openjdk.java.net/browse/JDK-8228631
> 
> Webrev:
> http://cr.openjdk.java.net/~kbarrett/8228631/open.00/
> 
> Testing:
> mach5 tier1
>