Updated example config to 'common' setup for federation operators

inventory/inventory

 # Inventory Aliases
 # Make sure to change group_vars/all.yml for the same hosts keys
-et2             ansible_host=et2.gndev.hexaa.eu ansible_user=ansible ansible_ssh_private_key_file=.ssh/id_ansible
-mdxcdn          ansible_host=mdxcdn.pt-38.utr.surfcloud.nl ansible_user=ansible ansible_ssh_private_key_file=.ssh/id_ansible
-alternative-mdx ansible_host=alternative-mdx.pt-76.utr.surfcloud.nl ansible_user=ansible ansible_ssh_private_key_file=.ssh/id_ansible
-okeanos         ansible_host=62.217.72.109 ansible_user=ansible ansible_ssh_private_key_file=.ssh/id_ansible
+mdx-signer      ansible_host=xxx.xxx.xxx.xxx ansible_user=debian ansible_ssh_private_key_file=~/.ssh/my_deploy_pubkey
+mdx-proxy-1     ansible_host=xxx.xxx.xxx.xxx ansible_user=debian ansible_ssh_private_key_file=~/.ssh/my_deploy_pubkey
+mdx-proxy-2     ansible_host=xxx.xxx.xxx.xxx ansible_user=debian ansible_ssh_private_key_file=~/.ssh/my_deploy_pubkey
 
 # Hosts that receive the mdsigner role
 [mdsigner]
-et2
-mdxcdn
-alternative-mdx
+mdx-signer
 
 # Hosts that receive the mdproxy role
 [mdproxy]
-et2
-mdxcdn
-alternative-mdx
-okeanos
+mdx-proxy-1
+mdx-proxy-2
 
 # Hosts that receive the GeoDNS role
 [geodns]
-et2
-mdxcdn
+mdx-proxy-1
+mdx-proxy-2
 
 # All hosts for base role
 [all:children]