Update the SolutionState's qs and bhp members.

This way they can be used instead of repeatedly extracting the top segment data,
which also could make it possible to use more of the existing implementation.

opm/autodiff/BlackoilMultiSegmentModel.hpp

@@ -202,6 +202,8 @@ namespace Opm {
 
         const std::vector<WellMultiSegmentConstPtr> wells_multisegment_;
 
+        std::vector<int> top_well_segments_;
+
         // return wells object
         // TODO: remove this wells structure
         using Base::wells;