hg: shenandoah/jdk: ClassUnloadingWithConcurrentMark should be opt-in with Shenandoah

[ashipile at redhat.com]

Changeset: a67a29f42b95
Author:    shade
Date:      2018-05-23 12:30 +0200
URL:       http://hg.openjdk.java.net/shenandoah/jdk/rev/a67a29f42b95

ClassUnloadingWithConcurrentMark should be opt-in with Shenandoah

! src/hotspot/share/gc/shenandoah/shenandoahArguments.cpp
! test/hotspot/jtreg/gc/shenandoah/options/TestClassUnloadingArguments.java