RFR: Hide is_concurrent_traversal_in_progress check under the type check

[Roman Kennke]

Am 06.04.2018 um 15:39 schrieb Aleksey Shipilev:
> http://cr.openjdk.java.net/~shade/shenandoah/alloc-hide-ha/webrev.01/
> 
> Micro-optimization: this avoid ShHeap field access on the usual path, instead checking on local
> variable.
> 
> Testing: hotspot_gc_shenandoah

Ok