RFR (S): 8183121: Add information about scanned and skipped cards during UpdateRS

[Thomas Schatzl]

Hi all,

  can I have reviews for this small change that adds some information
about how many cards were scanned/skipped during Update RS.

This information is much better than just the number of processed
buffers, although I kept them for now.

This change is based on Erik's changes for JDK-8183539.

CR:
https://bugs.openjdk.java.net/browse/JDK-8183121
Webrev:
http://cr.openjdk.java.net/~tschatzl/8183121/webrev
Testing:
jprt, test case

Thanks,
  Thomas