[NbtkGrid] clean up allocation
[NbtkGrid] clean up allocation

Chain up with the allocated size, but ignore the height if vadjustments are
set.

pwithnall/mx,jonnylamb/mx,clutter-project/mx,jonnylamb/mx,pwithnall/mx,pwithnall/mx,pwithnall/mx,jonnylamb/mx,jonnylamb/mx,clutter-project/mx,clutter-project/mx,clutter-project/mx