Clean up ECMap on deactivate

Change-Id: Ida08051f51abe3bf8dcb6ed52dfd64df92733671

@@ -189,6 +189,7 @@ public class UiExtensionManager
     @Deactivate
     public void deactivate() {
         prefs.removeListener(prefsListener);
+        prefs.destroy();
         UiWebSocketServlet.closeAll();
         unregister(core);
         log.info("Stopped");