If using namespaced fixtures, get following Ruby warning.
```
activerecord/lib/active_record/fixtures.rb:922: warning: method redefined; discarding old admin_foos
activerecord/lib/active_record/fixtures.rb:922: warning: previous definition of admin_foos was here
```
This is happening because of the multiple set the same path when setting the
fixture name. Fix to remove the duplicate path.
