no issue
- keep the original `ember-ajax` behaviour rather than returning `false` when we hit an ajax error - we should only be using `normalizeErrorResponse` to normalize our error responses 😉
- ensures our application code has access to the returned status code for ajax errors
refs #6207, #6207
- updates tests for new async behaviour
- fixes tests failing on validation errors
- fixes `feature.labs` not updating after successful save