RFR: 8221146: ZGC: Reports too much relocated

[Stefan Karlsson]

Hi all,

Please review this patch to fix the print outs of how much memory is 
about to be relocated.

http://cr.openjdk.java.net/~stefank/8221146/webrev.01/
https://bugs.openjdk.java.net/browse/JDK-8221146

Previously, we reported the size of all objects in all pages within the 
fragmentation limit. This patch fixes this, so that we only use the 
actually selected pages when determining the size.

Thanks,
StefanK