Set container_name as host_var in test inventory

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.

Change-Id: Ie39f2ef9c2f481479e6b73e88b6a7f27d8df8aea

tests/group_vars/all_containers.yml

@@ -13,7 +13,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-container_name: "{{ inventory_hostname }}"
 container_networks:
   management_address:
     address: "{{ ansible_host }}"

tests/host_vars/infra1.yml

@@ -16,3 +16,4 @@
 ansible_host: 10.1.0.2
 ansible_become: True
 ansible_user: root
+container_name: infra1

tests/host_vars/openstack1.yml

@@ -16,3 +16,4 @@
 ansible_host: 10.1.0.3
 ansible_become: True
 ansible_user: root
+container_name: openstack1