Refactors horizon setup section in osbash
Refactors horizon setup section in osbash

This patch changes some operations in the
setup_horizon script to match install-guides
and adds links to the section in install-guides.

Change-Id: If398389ca56e58d6959c4b3c3277878f403a1e20

openstack/training-labs,dguitarbite/OpenStack-Labs,openstack/training-labs,openstack/training-labs,dguitarbite/OpenStack-Labs,dguitarbite/OpenStack-Labs