RFR: Don't generate arraycopy pre-barrier calls for traversal GC

[Aleksey Shipilev]

On 06/18/2018 11:03 PM, Roman Kennke wrote:
> It turns out that some register shuffling is required in the prologue
> (in x86) to support the epilogue (gaaa). I moved the check to the if
> (!dest_unitialized) check to preserve that shuffling.
> 
> Passes tier3_gc_shenandoah now.
> 
> http://cr.openjdk.java.net/~rkennke/no-array-prebarrier-traversal/webrev.01/

OK!

-Aleksey