[bug fix] When recovering a post, at times the topic related to the post still returns nil.
Use the with_deleted method to include topics that have been soft deleted so that they too can
be recovered.
Update username should return a json response

- Have update username return json response that contains the updated
  username and id. I figured this would be better than just return "OK".
- Add test to verify that the new username is returned.
Merge pull request #3035 from oblakeerickson/update_username_return_json

Update username should return a json response
Merge pull request #3033 from verdi327/account_for_deleted_topic

[bug fix] Use with_deleted when looking up soft deleted topics for recovery