Default Ceph pg_num and pgp_num to 128

Default Ceph pg_num and pgp_num to 128

As per Ceph docs [1] we should default pg_num and pgp_num to 128 when
using less than 5 OSDs.

This same change was applied to the ceph-ansible profiles with [2].

Also updates the CI environment files to continue using 32 where we
deploy a single OSD.

1. http://docs.ceph.com/docs/master/rados/operations/placement-groups/
2. Ibd9fb23e04576e95e24af58f856663397886a947

Change-Id: I1920bc8f5251f362af38ad3bd6f46dda42c6ee93
Closes-Bug: #1718756
(cherry picked from commit e17ae7620e03790da0d29092ab42e8089b2e8d11)