handle both 'ansible_host' and 'ansible_ssh_host' in bastion configuration

'absible_ssh_host' is deprecated in Ansible 2.0 and at least
'contrib/inventory_builder/inventory.py' uses 'ansible_host' instead.

roles/bastion-ssh-config/templates/ssh-bastion.conf

@@ -4,7 +4,7 @@
 
 {% for h in groups['all'] %}
 {% if h != 'bastion' %}
-{% if vars.update({'hosts': vars['hosts'] + ' ' + hostvars[h]['ansible_ssh_host']}) %}{% endif %}
+{% if vars.update({'hosts': vars['hosts'] + ' ' + (hostvars[h].get('ansible_ssh_host') or hostvars[h]['ansible_host'])}) %}{% endif %}
 {% endif %}
 {% endfor %}
 
@@ -18,4 +18,4 @@ Host {{ bastion_ip }}
 Host {{ vars['hosts'] }}
   ProxyCommand ssh -W %h:%p {{ real_user }}@{{ bastion_ip }}
   StrictHostKeyChecking no
-{% endif %}
+{% endif %}