dashboard: remove "certificate is valid for" error

dashboard: remove "certificate is valid for" error

When deploying dashboard with ssl certificates generated by
ceph-ansible, we enforce the CN to 'ceph-dashboard' which can makes
application such alertmanager complain like following:

`err="Post https://mgr0:8443/api/prometheus_receiver: x509: certificate is valid for ceph-dashboard, not mgr0" context_err="context deadline exceeded"`

The idea here is to add alternative names matching all mgr/mon instances
in the certificate so this error won't appear in logs.

Closes: https://bugzilla.redhat.com/show_bug.cgi?id=1978869
Signed-off-by: Guillaume Abrioux <gabrioux@redhat.com>
(cherry picked from commit 72a0336c71cee8bd0a375ac47cb45a292844edc8)