adapt to python-novaclient-2.18.0

Novaclient renamed HTTPNotImplemented to HttpNotImplemented
and changed the attribute code to status in exceptions

This change should make the code work on newer and older versions.

Closes-Bug: #1340596
(cherry picked from commit 322004f8480e40af5e77ed843ff803005d5af27c)

Conflicts:
	openstack_dashboard/dashboards/project/instances/console.py
	openstack_dashboard/test/test_data/exceptions.py

Change-Id: Ifef6c4c1b2924b03df00f427cfe3e6a7f415e569