RFR: Cleanup SHH::should_start_normal_gc

[Aleksey Shipilev]

And this one!

-Aleksey

On 03/29/2018 10:37 AM, Aleksey Shipilev wrote:
> http://cr.openjdk.java.net/~shade/shenandoah/cleanups-shh-start-normal/webrev.01/
> 
> This cleans up should_start_concurrent_mark:
>  - renames to be consistent with partial/traversal
>  - eliminates excess arguments that most heuristics do not need
>  - purges ShenandoahConcMarkGC flag
> 
> Testing: hotspot_fast_gc_shenandoah
> 
> Thanks,
> -Aleksey
>