facts: fix external cluster bug
facts: fix external cluster bug

running an external ceph cluster deployment with (obviously) no
monitors defined in inventory breaks with an undefined error because
`_monitor_addresses` never get defined.

Closes: https://bugzilla.redhat.com/show_bug.cgi?id=1707460

Signed-off-by: Guillaume Abrioux <30a9df5a0293a6108675377fa1673f7aa713f915@redhat.com>

ceph/ceph-ansible,ceph/ceph-ansible