tests: disable test_mgr_dashboard_is_listening
tests: disable test_mgr_dashboard_is_listening

Due to a recent commit that has introduced a regression in ceph, this
test is failing.
Temporarily disabling it to unblock the CI.

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

ceph/ceph-ansible,ceph/ceph-ansible