ceph.spec.in: add new Requires from ceph-disk-prepare

Added new Requires from ceph-disk-prepare: cryptsetup, gptfdisk,
parted and util-linux.

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
Merge pull request #82 from dalgaaf/wip-da-spec

ceph.spec.in: add new Requires from ceph-disk-prepare

Reviewed-by: Sage Weil <sage@inktank.com>