Update Octario readme
Update Octario readme

While Octario is mostly used with InfraRed, there is nothing about it
in the readme which should instruct how to install and run Octario.

Also, several testers no longer supported by Octario and were removed
from readme.

Change-Id: I92b39265175d4c581a0514dda354e881705846b6

redhat-openstack/octario,redhat-openstack/octario