Add ansible.cfg

Pipelining makes ansible run tasks much faster, and as of Ansible
2.0 or 2.1 or so, it now works on older hosts that have requiretty
in their sudo config[0]. Also, disable the creation of those stupid
retry files.

[0] https://github.com/ansible/ansible/pull/13200

ansible.cfg

@@ -0,0 +1,3 @@
+[defaults]
+pipelining=True
+retry_files_enabled=False