Revert "Applied fix for #4283"

This reverts commit 7f3e956.

Author: timlinux

src/core/composer/qgscomposermap.cpp

@@ -360,11 +360,6 @@ void QgsComposerMap::paint( QPainter* painter, const QStyleOptionGraphicsItem* i
 
 void QgsComposerMap::updateCachedImage( void )
 {
-  //If we have a locked layer set then don't reload the map canvas.
-  if ( mKeepLayerSet )
-  {
-    return;
-  }
   syncLayerSet(); //layer list may have changed
   mCacheUpdated = false;
   cache();