Use member.profile.display_name instead of member.display_name for profile images alt attribute

Ghost User
2018-11-05T20:10:28+01:00

1. Go to user profile page.
2. Look at `alt` attribute of the profile image.
3. It is not the `display_name`.

#### New behaviour
Steps to validate that it works:

1. Go to user profile page.
2. Look at `alt` attribute of the profile image.
3. It is the `display_name` (or the username if there is no `display_name`).