ceph-disk: use the type file for bluestore

ceph-disk: use the type file for bluestore

The type file in the OSD bluestore data exists and contains the
bluestore string. ceph-disk activate should use it instead of
the "osd objectstore" configuration value. It is better in case the
configuration file changes between prepare and activate.

The fsid file cannot be used by bluestore to signify that ceph-osd
--mkfs has completed successfully because it is pre-populated by
ceph-disk. Introduce the mkfs_done file, dedicated to this, instead of
overloading an existing file.

Signed-off-by: Sage Weil <sage@redhat.com>
Signed-off-by: Loic Dachary <loic@dachary.org>