Add upgrade-horizon

Upgrade horizon along with the rest of devstack before running new
devstack tests and tempest.

upgrade-horizon is based off of upgrade-keystone.

Change-Id: I6a6e4da06806cb840d7af673673e06f34eb297e0
Related-Bug: #1265057
(cherry picked from commit e9546e66e6236a1e2c79734ee0c9dcb0cc50bbb3)
Merge "Add upgrade-horizon" into stable/havana