Corrected parameter for sorting on search grid

The nbnxn grid search sorting range parameter used the whole box
height instead of the local DD cell height with domain decomposition
along z. This could not cause errors, but the search used O(N^2) time
with more than 4 domains along z, instead of O(N).

Change-Id: I324df6b15635a5ecff7c8bfeb124fdb933e5f845