[vector] Fix variable shift count amount

[Paul Sandoz]

> On May 22, 2018, at 3:58 PM, Lupusoru, Razvan A <razvan.a.lupusoru at intel.com> wrote:
> 
> Thanks for looking at this Paul. I will update the patch to use SPECIES instead of calling the species method.
> 

Ok, thanks.

> Regarding whether it makes sense to set them like zero - I do not think that will be useful. From an optimized code point of view, we want to initialize them with a broadcast because that way, there is no global object that needs unboxed. Even now, ZERO is not actually used in any intrinsic implementation other than the default implementation.
> 

Ok.

Paul.