[openstack-common] installation of liberty on Ubuntu 14.04 problem with PPA

[Marcin Karkocha]

openstack-common recipe has issue with updating ubuntu repositories in installation on ubuntu trusty.
Trying to change components list allways give me result with "trusty" value which make this error:
`deb "http://ubuntu-cloud.archive.canonical.com/ubuntu" trusty trusty-proposed/liberty main`

part of log with error is here: http://paste.openstack.org/show/495504/

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/liberty
Review: https://review.openstack.org/310875

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/310875
Committed: https://git.openstack.org/cgit/openstack/cookbook-openstack-common/commit/?id=30e554a939a59d9a1bfe52d842138beda94b825a
Submitter: Jenkins
Branch: stable/liberty

commit 30e554a939a59d9a1bfe52d842138beda94b825a
Author: Samuel Cassiba <email address hidden>
Date: Thu Apr 28 13:08:02 2016 -0500

    Split apt_components for bare metal provisioning

    The openstack-ppa.list file gets generated with an extra 'trusty'
    resulting in a failed convergence on bare metal nodes.

    Change-Id: Id34676333ecb383367e127557104bc134a9bfb1d
    Closes-Bug: #1575613