ceph-disk-activate: pull mount options from ceph.conf

Signed-off-by: Alexandre Marangone <alexandre.marangone@inktank.com>
(cherry picked from commit e21e751ecb2a175c616b5e1e3977baf205cd9736)
ceph-disk-prepare: always force mkfs.xfs

Signed-off-by: Alexandre Marangone <alexandre.marangone@inktank.com>
(cherry picked from commit 5f32f986314175d0b9561b44615601ba62f82bd8)