Mark wells with negative and trivial potentials as not operable

The simulator will try to compute potentials at every iterations to
try to reopen the well.

opm/simulators/wells/BlackoilWellModelGeneric.hpp

@@ -396,6 +396,8 @@ protected:
                               const SummaryConfig& summaryConfig,
                               DeferredLogger& deferred_logger);
 
+    bool guideRateUpdateIsNeeded() const;
+
     // create the well container
     virtual void createWellContainer(const int time_step) = 0;
     virtual void initWellContainer() = 0;