Improve validation of active/selected state of elements
The following discussion from gitlab-ce!21846 should be addressed:
In reference to code like `has_css?(".active", text: 'Sign in')`
- [ ] @ddavison started a [discussion](https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/21846#note_103544980): (+1 comment)
> we'll have to figure out a better way to do this sort of validation later.
>
> most likely with the [new wait class](gitlab-ce!20185) .
issue