[Bugfix][Symbology] Fill to SLD does not export Stroke color

The commit 2f268d4 fixing the way SLD is exporting size, from mm to pixels. But in the case of exporting line to SLD the stroke color has not been preserved.

src/core/symbology-ng/qgsfillsymbollayerv2.cpp

@@ -353,7 +353,7 @@ void QgsSimpleFillSymbolLayerV2::toSld( QDomDocument &doc, QDomElement &element,
     QDomElement strokeElem = doc.createElement( "se:Stroke" );
     symbolizerElem.appendChild( strokeElem );
     double borderWidth = QgsSymbolLayerV2Utils::rescaleUom( mBorderWidth, mBorderWidthUnit, props );
-    QgsSymbolLayerV2Utils::lineToSld( doc, strokeElem, mBorderStyle, borderWidth, borderWidth, &mPenJoinStyle );
+    QgsSymbolLayerV2Utils::lineToSld( doc, strokeElem, mBorderStyle, mBorderColor, borderWidth, &mPenJoinStyle );
   }
 
   // <se:Displacement>