Add ini-suffix to inventory file to make the filetype clear

This change further changes the name of the only host in question form
localhost to "127.0.0.1" to resolve the annoying warning about the
duplicated declaration of "localhost" at the start of the execution of
the playbook.

ansible.cfg

@@ -1,6 +1,6 @@
 [defaults]
 nocows = True
-inventory = inventory
+inventory = inventory.ini
 become = True
 ask-become-pass = True
 display_skipped_hosts = False

inventory

@@ -1,2 +0,0 @@
-[localhost]
-localhost ansible_connection=local

inventory.ini

@@ -0,0 +1,2 @@
+[localhost]
+127.0.0.1 ansible_connection=local