Fix status_code not passed in code

The python-neutronclient was refactored to raise NeutronClientException
and when that occured the status_code field was dropped. This causes errors
on the nova-side to occur as nova checks the status_code to do error handling.

Fixes bug: 1245700

Change-Id: Ie1fcf3fef0e20c33ce18549bca6a2413a9f98e9f