hg: jdk/jdk14: 8235751: Assertion when triggering concurrent cycle during shutdown

[kim.barrett at oracle.com]

Changeset: 6e51a868361e
Author:    kbarrett
Date:      2020-01-07 17:28 -0500
URL:       https://hg.openjdk.java.net/jdk/jdk14/rev/6e51a868361e

8235751: Assertion when triggering concurrent cycle during shutdown
Summary: Skip initial mark during shutdown and don't assert when that happens.
Reviewed-by: sjohanss, tschatzl

! src/hotspot/share/gc/g1/g1CollectedHeap.cpp
! src/hotspot/share/gc/g1/g1VMOperations.cpp
! src/hotspot/share/gc/g1/g1VMOperations.hpp