gate-sahara-buildimages-ambari job fix
gate-sahara-buildimages-ambari job fix

This job has been failing because we use ubuntu as base image OS
which is not supported in ambari version <= 2.1.1

Change-Id: I5feb11d94435bd48b8116be3986e588fca16f47c
Closes-bug: 1540318

openstack/sahara-image-elements,openstack/sahara-image-elements