Fix SHUT wells

Shut wells are not added to the well list and thus not considered in the
simulator.

The shut well test in test_wellsmanager is modified to assert this
behaviour.

BUG: This change provokes an assert in the EclipeWriter as number of
wells in wellstate is different from number of wells in the schedule.

opm/core/wells/WellsManager.cpp

@@ -412,7 +412,7 @@ namespace Opm
             }
 
             if (well->getStatus(timeStep) == WellCommon::SHUT) {
-                well_controls_shut_well( w_->ctrls[well_index] );
+                //well_controls_shut_well( w_->ctrls[well_index] );
                 well_index++;
                 continue;
             }