Profile picture doesn't always show next to comment

Original 3akai-ux report:

This problem happens when taking the following steps:

1. Log in as a user with a profile picture (make sure caching is enabled)
2. Upload a PDF
3. Go to the content profile page
4. Try to make a comment
5. The new comment has no profile picture

![screen shot 2014-02-11 at 20 16 51](https://f.cloud.github.com/assets/109850/2141471/891f9c7a-9359-11e3-9f42-62ff4dccaa21.png)

After some investigation:

When '/api/' + resourceType + '/' + id + '/messages' is fetched all resulting users that have a profile picture have the following properties:
![screen shot 2014-02-12 at 09 14 01](https://f.cloud.github.com/assets/218391/2146731/111224ba-93c6-11e3-9a6f-2cd7cee73dd4.png)

When a comment or reply is added the returned comment object doesn't have the `medium` and `small` properties.
![screen shot 2014-02-12 at 09 15 08](https://f.cloud.github.com/assets/218391/2146739/3336a336-93c6-11e3-991e-2ad0909fe2de.png)

https://github.com/oaeproject/Hilary/blob/master/node_modules/oae-content/lib/api.js#L1692 is a suspect.