RFR (XS): 8139874: After G1 Full GC, the next GC is always a young-only GC

[Thomas Schatzl]

Hi all,

  can I have reviews for this small change that makes the transition
from Full GC to a marking cycle faster? This helps in memory tight cases
(of just if the IHOP is messed up) when a full gc yields less space than
the IHOP value, hopefully avoiding further gcs.

CR:
https://bugs.openjdk.java.net/browse/JDK-8139874
Webrev:
http://cr.openjdk.java.net/~tschatzl/8139874/webrev/
Testing:
jprt, vm.gc testlist, manual testing

Thanks,
  Thomas