RFR: 8065227: Report allocation context stats at end of cleanup

[Stefan Johansson]

Hi,

Please review this small fix for:
https://bugs.openjdk.java.net/browse/JDK-8065227

Webrev:
http://cr.openjdk.java.net/~sjohanss/8065227/hotspot.00/

Summary:
The update for the allocation context has previously been done in the 
remark phase but this is a little to early. The last stw-phase of the 
marking cycle is the cleanup and if doing the reporting there that 
simplifies.

Thanks,
Stefan