RFR(S): 8237776: Shenandoah: Wrong result with Lucene test

[Roland Westrelin]

> - Fix is not in Shenandoah code, but shared. Even though only Shenandoah
> currently seems to fall over it. Also, should probably draw attention of
> non-Shenandoah reviewers...

Fix IS in shenandoah code.

Roland.