looks like there may be a simpler approach using latest mockwebserver.  scroll to the bottom of this: http://code.google.com/p/mockwebserver/issues/detail?id=7  Basically, it looks like you can use a normal ref instead of an atomic one.
ex.
```
server.play();
final URL url = server.getUrl();
server.setDispatcher(new URLReplacingQueueDispatcher(url)); // where impl of URLReplacingQueueDispatcher is this code
try {
...
```