improve map's getLayer() function, includes improved test. cheers to pensyakito for bringing this up and to cr5 for the review (Closes #861)

git-svn-id: http://svn.openlayers.org/trunk/openlayers@5221 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Map.js

@@ -475,6 +475,7 @@ OpenLayers.Map = OpenLayers.Class({
             var layer = this.layers[i];
             if (layer.id == id) {
                 foundLayer = layer;
+                break;
             }
         }
         return foundLayer;