RFR (S) 8242625: Shenandoah: restore heap logging for Degenerated/Full cycles

[Aleksey Shipilev]

Bug:
  https://bugs.openjdk.java.net/browse/JDK-8242625

This is another logging regression since JDK-8241984. Fix is similar to what JDK-8242400 done:
  https://hg.openjdk.java.net/jdk/jdk/rev/7992ff451fec

Webrev:
  https://cr.openjdk.java.net/~shade/8242625/webrev.01/

Testing: eyeballing gc logs, hotspot_gc_shenandoah (running)

-- 
Thanks,
-Aleksey