Assume begin_cell_centroid to what the name tells us: an iterator over then centroids.

Therfore we do not need to call center() in getCoordinate. This is done in the iterator
class returned from CpGrid.

opm/core/props/satfunc/SaturationPropsFromDeck_impl.hpp

@@ -494,7 +494,7 @@ namespace
     template<class T>
     double getCoordinate(T t, int i)
     {
-        return t->center()[i];
+        return (*t)[i];
     }