The connection plugin no longer falls back on using the
inventory_hostname as the container_name. Set container_name as a host
var for each container in the test inventory.
In this role's case there are no containers, so I've just removed
the group_var so that the test setup is uniform with other roles
which do use containers.
Change-Id: Ifde552c38d219ede46f3c4c8091e38048205d02f