Use glance as a backend for Solum LanguagePack API (GET Method)

Replace the implementation of GET method of LanguagePack API.
A GET on LanguagePack will query glance with the id provided and
retrieve LP attributes from Glance image tags.

This patch also deactivate functionnal tests for LP. They will be
enabled again when the LP API has been fully moved to "Glance".

Fixes bug 1301440

Change-Id: Ied7942da32577eca883d29b06c60a8f0da18e0d5
Merge "Use glance as a backend for Solum LanguagePack API (GET Method)"