ceph-osd: exit gracefully when no data partition

ceph-osd: exit gracefully when no data partition

When using collocated or non-collocated osd_scenarios (ceph-disk) and
trying to deterime the OSD_DEVICE from the OSD_ID passed to the systemd
unit then we can be in a situation where the OSD hasn't been activated
but the OSD ID exists.
This means the data partition isn't in activate state and the ceph-disk
list command won't show the OSD ID on the data partition.

Closes: https://bugzilla.redhat.com/show_bug.cgi?id=1850377
Signed-off-by: Dimitri Savineau <dsavinea@redhat.com>