ceph::key: ceph-authtool is part of ceph-common

Since ceph-authtool is part of ceph-common make sure the package
gets installed.

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
(cherry picked from commit 754f8fbc3c6a1888e5a527a5efb0a99604ca04d2 from
https://github.com/dalgaaf/puppet-ceph/tree/feature/wip-da-rework-and-simplify)