Config API node needs to have facts to check if it is Linux

For code:
  when:
    - ('vrouter' in node_roles_dict[instance_name].deleted_roles)
    - ansible_system == 'Linux'

in playbooks/roles/contrail/tasks/deregister.yml

Closes-Bug: #1788447

Change-Id: I4146ec4db43e62178d7b120b1b747dcb14fd7adb

playbooks/install_contrail.yml

@@ -28,7 +28,7 @@
 
 - name: Remove Contrail from Deleted Nodes ( Deregister )
   hosts: container_hosts
-  gather_facts: no
+  gather_facts: yes
   tasks:
   - include_role:
       name: contrail