historyProperties(): Extract BHP limit if not defaulted

This fixes a programming error introduced in the refactoring of
Schedule::handleWCONProducer() (commit 3889e92).  When there is a BHP
limit in WCONHIST, we obviously need the value specified in the input
deck.  The refactoring led to the limit being extracted only in the
prediction mode.

Pointy hat: [at] bska

opm/parser/eclipse/EclipseState/Schedule/Schedule.cpp

@@ -195,6 +195,8 @@ namespace Opm {
 
             // BHP mode needs explicit value
             if (! record->getItem("BHP")->defaultApplied()) {
+                p.BHPLimit = record->getItem("BHP")->getSIDouble(0);
+
                 p.addProductionControl(WellProducer::BHP);
             }