Federation: Don't serve distant resource Data

Related: djangoldp-account#43 (closed)

Currently, distant resource are also served on local container. It leads to duplicate & glitched content, they should not, they must contain only their @id without anything else.

See: https://api.test2.startinblox.com/users/ & https://api.test1.startinblox.com/users/jbpasquier/