Create page with instructions for upgrading Havana to Icehouse in Ubuntu

[Igor D.C.]

Icehouse has already been released.

Currently, this page: http://docs.openstack.org/trunk/openstack-ops/content/ops_upgrades_grizzly_havana-ubuntu.html has some instructions to upgrade from Grizzly to Havana in Ubuntu.
However, there isn't yet anything regarding the upgrade from Havana to Icehouse, in a similar fashion as the above link.

This bug report wants to address that by creating a new page, with similar formatting and steps as the Grizzly->Havana one, but taking into account the following points.
- Havana->Icehouse specific;
- Considering Neutron as well;
- Considering the special and popular case of OVS to ML2 migration;
- Ubuntu 12.04 LTS only, _for now_.

The page would then be added to http://docs.openstack.org/trunk/openstack-ops/content/ch_ops_upgrades.html, like the Grizzly->Havana one is.

The Grizzly->Havana page will be kept, in case users want to migrate from Grizzly to Icehouse indirectly (which is also more reliable).

[Igor D.C. (igordcard)]

Assigned to me.

[Openstack Gerrit (openstack-gerrit)]

Fix proposed to branch: master
Review: https://review.openstack.org/91626

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/91626
Committed: https://git.openstack.org/cgit/openstack/operations-guide/commit/?id=151bb456681b76f90dda55859fd131d03c9d394b
Submitter: Jenkins
Branch: master

commit 151bb456681b76f90dda55859fd131d03c9d394b
Author: Igor Duarte Cardoso <email address hidden>
Date: Thu May 29 19:47:09 2014 +0000

    Adds instructions to upgrade Havana to Icehouse

    Adds instructions to upgrade Havana to Icehouse in Ubuntu 12.04.4 LTS,
    placed inside Operations/Upgrades, right below the Grizzly to Havana
    upgrade instructions for RHEL.
    These upgrade instructions intend to have similar formatting and steps
    as the Grizzly->Havana ones, but taking into account the following:
    - Be Havana->Icehouse specific;
    - Considering Neutron as well;
    - Considering the special and popular case of OVS to ML2 migration;
    - Ubuntu 12.04 LTS only, _for now_.

    Change-Id: I8d3cce0a2ceb306174c37d92382e201ff545be60
    Closes-Bug: #1312660
    Co-Authored-By: Matt Kassawara <email address hidden>