dashboard: always set `dashboard_server_addr`
dashboard: always set `dashboard_server_addr`

When running the playbook with `--limit`, if the play targeted doesn't match
hosts present in the mgr group the playbook can fail.

Closes: https://bugzilla.redhat.com/show_bug.cgi?id=2063029

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

ceph/ceph-ansible,ceph/ceph-ansible