RFR (XS): JDK-8047976: Ergonomics for GC thread counts should update the flags

[Sangheon Kim]

Hi all,

can I have reviews for the following small change to update 
G1ConcRefinementThreads variable?
And also I need a sponsor for this.

CR:
https://bugs.openjdk.java.net/browse/JDK-8047976

Webrev:
http://cr.openjdk.java.net/~brutisso/8047976/webrev.00/ 
<http://cr.openjdk.java.net/%7Ebrutisso/8047976/webrev.00/>

Testing: jprt

Thanks,
Sangheon