Add os_client_config_cloud parameter to infra_config.yml

Instead of hardcoding to a known clouds.yaml cloud name, allow
it to be configurable.

infra_config.yml.sample

@@ -1,4 +1,5 @@
 ---
+os_client_config_cloud: envvars
 system_config_repo_url: git@your_git_server/system-config.git
 key_name: your_openstack_key
 domainname: yourdomain

roles/provision_infra_servers/tasks/main.yml

@@ -2,8 +2,8 @@
 - name: Create OpenStack instances
   os_server:
     state: present
-    cloud: openstack
-    name: "{{ item.name }}"
+    cloud: "{{os_client_config_cloud}}"
+    name: "{{ item.name }}.{{ domainname }}"
     region_name: region-b.geo-1
     availability_zone: az2
     image: "{{ item.image }}"