Layer.Vector.removeMap must deactivate the strategies, r=fredj (closes #1649)

git-svn-id: http://svn.openlayers.org/trunk/openlayers@7708 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Strategy/Fixed.js

@@ -39,13 +39,20 @@ OpenLayers.Strategy.Fixed = OpenLayers.Class(OpenLayers.Strategy, {
      * Method: activate
      * Activate the strategy: reads all features from the protocol and add them 
      * to the layer.
+     *
+     * Returns:
+     * {Boolean} True if the strategy was successfully activated or false if
+     *      the strategy was already active.
      */
     activate: function() {
-        OpenLayers.Strategy.prototype.activate.apply(this, arguments);
-        this.layer.protocol.read({
-            callback: this.merge,
-            scope: this
-        });
+        if(OpenLayers.Strategy.prototype.activate.apply(this, arguments)) {
+            this.layer.protocol.read({
+                callback: this.merge,
+                scope: this
+            });
+            return true;
+        }
+        return false;
     },
 
     /**