openstack-ardana: do not store host keys on known_hosts
openstack-ardana: do not store host keys on known_hosts

Ansible is storing host keys on ssh known_hosts files wich cause
issues when the same IP is used for different hosts (virtual envs
- [1]).

This change adds UserKnownHostsFile=/dev/null to ansible ssh_args
so those host keys won't be stored.

1. https://ci.suse.de/job/openstack-ardana-vcloud/733/console

gosipyan/automation,aspiers/automation,SUSE-Cloud/automation,gosipyan/automation,aspiers/automation,gosipyan/automation,aspiers/automation,SUSE-Cloud/automation,aspiers/automation,SUSE-Cloud/automation,gosipyan/automation,SUSE-Cloud/automation