Bug 1215872
Add a relationship with eager loading in the Port and Network models,
thus preventing the 'extend' functions from performing extra queries.
This patch also slight alters the methods for processing qos_queue
bindings in order to allow them for populating the qos_queue id in
the response being created.
Change-Id: Ie80d12aeed5de94afa61f23d7bcfc21372f23c4f