Add ansible.cfg file

* set the default hosts file
* disable retry files by default
* always show the diff

Also edited README to remove -i
6 jobs for add_ansible_cfg in 39 seconds (queued for 1 second)
Status Job ID Name Coverage
  Galaxy
passed #4623
preprod
galaxy:install

00:00:32

 
  Test Syntax
passed #4626
preprod
syntax:check

00:00:03

failed #4624
preprod
syntax:check

00:00:02

 
  Test Ansible
failed #4657
preprod
ansible:check

00:00:03

failed #4627
preprod
ansible:check

00:00:02

failed #4625
preprod
ansible:check

00:00:03

 
Name Stage Failure
failed
ansible:check Test Ansible
PLAY [all] *********************************************************************

TASK [Gathering Facts] *********************************************************
fatal: [pi3.lqdn.fr]: UNREACHABLE! => {"changed": false, "msg": "Failed to connect to the host via ssh: Host key verification failed.\r\n", "unreachable": true}

PLAY RECAP *********************************************************************
pi3.lqdn.fr : ok=0 changed=0 unreachable=1 failed=0

ERROR: Job failed: exit status 1