Trim legacy variable usage.

library/inventory/add_host

@@ -24,13 +24,13 @@ author: Seth Vidal
 
 EXAMPLES = '''
 # add host to group 'just_created' with variable foo=42
-- add_host: name=${ip_from_ec2} groups=just_created foo=42
+- add_host: name={{ ip_from_ec2 }} groups=just_created foo=42
 
 # add a host with a non-standard port local to your machines
-- add_host: name='${new_ip}:${new_port}' 
+- add_host: name={{ new_ip }}:{{ new_port }}
 
 # add a host alias that we reach through a tunnel
-- add_host: hostname=${new_ip}
-            ansible_ssh_host=${inventory_hostname}
-            ansible_ssh_port=${new_port}
+- add_host: hostname={{ new_ip }}
+            ansible_ssh_host={{ inventory_hostname }}
+            ansible_ssh_port={{ new_port }}
 '''