update: fix a typo
update: fix a typo

`hostvars[groups[mon_host]]['ansible_hostname']` seems to be a typo.
That should be `hostvars[mon_host]['ansible_hostname']`

Signed-off-by: Guillaume Abrioux <30a9df5a0293a6108675377fa1673f7aa713f915@redhat.com>
(cherry picked from commit 7c99b6df6d8f0daa05ed8da987984d638af3a794)

fgal/ceph-ansible,fgal/ceph-ansible