defaults: change defaults value

defaults: change defaults value

this commit changes defaults value in default pool definitions.

there's no need to define `pg_num`, `pgp_num`, `size` and `min_size`,
`ceph_pool` module will use the current default if needed.

This also drops the 3 following `set_fact` in `ceph-facts`:

- osd_pool_default_pg_num,
- osd_pool_default_pgp_num,
- osd_pool_default_size_num

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