emitting to a room doesn't work for namespaced clients

## Failing

```
io.of('/foo').on('connection', function(client) {
  client.join('aaa');
  this.in('aaa').emit('goes to noone since packet endpoint is set to "/foo/aaa", instead of "/foo" and room: "aaa"')
})
```
## Working

```
io.of('').on('connection', function(client) {
  client.join('aaa');
  this.in('aaa').emit('goes to aaa members since packet endpoint is set to "aaa"')
})
```
