tests: change cephfs pool size
tests: change cephfs pool size

`all_daemons` scenario can't handle pools with `size: 3` because we have
1 osd node in root=HDD and two nodes in root=default.

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

ceph/ceph-ansible,ceph/ceph-ansible