Add CI test layouts

* Drop Trusty from test matrix
* Add extra cases to test separate roles deployment

Signed-off-by: Bogdan Dobrelya <bdobrelia@mirantis.com>

tests/templates/inventory-gce.j2

@@ -2,6 +2,16 @@ node1 ansible_ssh_host={{gce.instance_data[0].public_ip}}
 node2 ansible_ssh_host={{gce.instance_data[1].public_ip}}
 node3 ansible_ssh_host={{gce.instance_data[2].public_ip}}
 
+{% if mode == "separate" %}
+[kube-master]
+node1
+
+[kube-node]
+node2
+
+[etcd]
+node3
+{% else %}
 [kube-master]
 node1
 node2
@@ -14,6 +24,7 @@ node3
 [etcd]
 node1
 node2
+{% endif %}
 
 [k8s-cluster:children]
 kube-node