Omit link to generate labels if user does not have access to create them

On a project that has no labels, a user was provided a link to create labels on the "Labels" tab, resulting in a 404. This MR changes the next to "No labels created" if the user lands on this page but does not have permission to add a label.

Screenshot:

![image](https://gitlab.com/stanhu/gitlab-ce/uploads/cb04659cf3a0abe1e072cb78d0964b94/image.png)

Closes https://github.com/gitlabhq/gitlabhq/issues/8353

See merge request !752