RFR: JDK-8229002: Shenandoah: Missing node types in ShenandoahLoadReferenceBarrier::needs_barrier_impl()

[Roman Kennke]

JDK11 testing brought up some missing cases in our C2 optimizer. Those
are trivial and non-fatal because we do the conservative thing there
anyway. But they hold up testing.

http://cr.openjdk.java.net/~rkennke/JDK-8229002/webrev.00/

Testing: hotspot_gc_shenandoah

Ok to push to jdk/jdk?

I would also like to cherry-pick this straight into shenandoah/jdk11 to
unbreak testing. Ok with that too?

Roman