Don't continually refresh map while editing rule label/desc

(cherry-picked from 2c3548d)

Author: nyalldawson

src/gui/symbology-ng/qgsrulebasedrendererv2widget.cpp

@@ -649,8 +649,8 @@ QgsRendererRulePropsWidget::QgsRendererRulePropsWidget( QgsRuleBasedRendererV2::
   connect( btnExpressionBuilder, SIGNAL( clicked() ), this, SLOT( buildExpression() ) );
   connect( btnTestFilter, SIGNAL( clicked() ), this, SLOT( testFilter() ) );
   connect( editFilter, SIGNAL( textChanged( QString ) ), this, SIGNAL( widgetChanged() ) );
-  connect( editLabel, SIGNAL( textChanged( QString ) ), this, SIGNAL( widgetChanged() ) );
-  connect( editDescription, SIGNAL( textChanged( QString ) ), this, SIGNAL( widgetChanged() ) );
+  connect( editLabel, SIGNAL( editingFinished() ), this, SIGNAL( widgetChanged() ) );
+  connect( editDescription, SIGNAL( editingFinished() ), this, SIGNAL( widgetChanged() ) );
   connect( groupSymbol, SIGNAL( toggled( bool ) ), this, SIGNAL( widgetChanged() ) );
   connect( groupScale, SIGNAL( toggled( bool ) ), this, SIGNAL( widgetChanged() ) );
   connect( mScaleRangeWidget, SIGNAL( rangeChanged( double, double ) ), this, SIGNAL( widgetChanged() ) );