library/ceph_pool: Fix potential null value when creating pools
library/ceph_pool: Fix potential null value when creating pools

Before, creating a pool by providing *only* `pg_num` would result in an
error as it would produce `--pgp-num null`.

This commit fix this behavior by defaulting `pgp_num` value to `pg_num`.

Signed-off-by: Mathias Chapelain <a25b9ce6392e903c28b85534d39c9f80ed302af2@proton.ch>

ceph/ceph-ansible,ceph/ceph-ansible