LB returns 422 if the LB has been deleted - ignore this error and continue deleting
Change callbacks to be more functional (thanks @manishtomar)
Merge branch 'master' of github.com:rackerlabs/otter into good-lb-errors
Use mock_treq, thanks @manishtomar
Merge pull request #548 from rackerlabs/good-lb-errors

AS-30 - delete server if LB has been deleted