Invalidate the layer cache when rolling back so that it draws correctly afterwards

git-svn-id: http://svn.osgeo.org/qgis/trunk/qgis@11841 c8812cc2-4d05-0410-92ff-de0c093fc19c

Author: timlinux

src/core/qgsvectorlayer.cpp

@@ -3094,6 +3094,9 @@ bool QgsVectorLayer::rollBack()
   emit editingStopped();
 
   setModified( FALSE );
+  // invalidate teh cache so the layer updates properly to show its original 
+  // after the rollback
+  setCacheImage( 0 );
   triggerRepaint();