As from OpenStack Ocata calls to novaclient.v2.contrib.instance_action
and novaclient.v2.contrib.list_extensions are deprecated
in favour of novaclient.v2.instance_action and
novaclient.v2.list_extensions respectively
Closes-bug: #1661767
Change-Id: I75d89a897093ef24fdb7f2c4a7c29c00fb3b2327
(cherry picked from commit 900a46064e)