openstack-ansible-aio doesn't work on Ubuntu 16.04. The error message
when executing `# scripts/run-playbooks.sh` will look like this:
TASK: [lxc_hosts | Gather variables for each operating system]
failed: [aio1] => {"failed": true, "item": null}
msg: No source file given
FATAL: all hosts have already failed -- aborting
There was an IRC discussion which stated the upper version the
stable/mitaka release supports for Ubuntu:
http://eavesdrop.openstack.org/irclogs/%23openstack-ansible/
%23openstack-ansible.2016-05-16.log.html#t2016-05-16T18:48:13
This change updates the docs to make that relationship clear.
Change-Id: Ia9060ebce6ca568f06e14b964700800d0ea8a6b1