manifests/conf.pp: fix documentation for auth_type

There are two allowed values for auth type in ceph: none and cephx.

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
add config options for signatures in ceph

Added the following config options to enable cephx signatures:
- cephx require signatures
- cephx cluster require signatures
- cephx service require signatures
- cephx sign messages

These options are optional.

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>