RFR (XS): 8183538: UpdateRS phase should claim cards

[Thomas Schatzl]

Hi all,

  please review this small change that adds claiming of cards in the
update rs phase so that scan rs does not rescan them.

CR:
https://bugs.openjdk.java.net/browse/JDK-8183538
Webrev:
http://cr.openjdk.java.net/~tschatzl/8183538/webrev/
Testing:
jprt

Thanks,
  Thomas