RFR: JDK-8240315: Shenandoah: Rename ShLBN::get_barrier_strength()

[Roman Kennke]

>> http://cr.openjdk.java.net/~rkennke/JDK-8240315/webrev.01/
> 
> Looks good, but there are some leftovers in ASSERT section.
> 
> Better yet?
>   https://cr.openjdk.java.net/~shade/shenandoah/8240315-add.patch

That looks even better, indeed. Thank you! I'm going to push this
combined change then:

http://cr.openjdk.java.net/~rkennke/JDK-8240315/webrev.02/

Thanks, Roman