Ceph OSD restart failure while upgrading from Stein to Train

* What happened:
While upgrading OpenStack from Stein to Train, in setup-infrastructure step (openstack-ansible ceph-install.yml playbook), ceph OSDs fails to restart and systemd journal shows these error messages:

Jan 23 10:57:30 dm1osstorage1a ceph-osd[4250]: server name not found: [v2:xx.xxx.210.11:3300 (Name or service not known) Jan 23 10:57:30 dm1osstorage1a ceph-osd[4250]: unable to parse addrs in [v2:xx.xxx.210.11:3300,v1:xx.xxx.210.11:6789],[v2:xx.xxx.210.73:3300,v1:xx.xxx.210.73:6789],[v2:xx.xxx.210.196:3300,v1:xx.xxx.210.196:6789]'

Three OSD are running on three dedicated hosts, MON and MGR are deployed on the three OpenStack controller/infra nodes.

* What I expected to happen:
OSDs upgraded to Nautilus, up and running.

* How to reproduce it:
Upgrade an OpenStack/Ceph deployment from Stein to Train, with OSA 20.0.1.

* Environment:
  - OS (deployment and target hosts): CentOS 7
  - openstack-ansible version: 20.0.1

NOTE: a ceph-ansible issue has been opened on Github (https://github.com/ceph/ceph-ansible/issues/4981) but the team said that special actions have to be performed when upgrading from Luminous or Mimic to Nautilus, and these actions are not performed by openstack-ansible. The team also said that a dedicated playbook is provided for that: rolling_update.yml.