Send HTTP exceptions in the format expected by neutronclient

Neutron client for the v2 API expects exceptions to have 'type',
'message' and 'detail' attributes. That is why they need to be
included in the body of HTTP Exceptions.

Change-Id: I70bd47977e42ad7bac760600329e9440452b74bc
Closes-Bug: 1355902
Merge "Send HTTP exceptions in the format expected by neutronclient"