RFR: 8194681: G1 uses young free cset time when reporting non-young free cset times

[Leo Korinth]

Hi,

G1 uses young free cset time when reporting non-young free cset times. 
This patch is fixing the typo.

Bug:
https://bugs.openjdk.java.net/browse/JDK-8194681

Webrev:
http://cr.openjdk.java.net/~lkorinth/8194681/00/

Testing:
- hs-tier1, hs-tier2

Thanks,
Leo