ceph-volume: Refactor is_ceph_device to simplify error handling

ceph-volume: Refactor is_ceph_device to simplify error handling

Replace the try-except block with a direct get() call on lv.tags to
check for ceph.osd_id. This avoids catching AttributeError unnecessarily
and makes the logic more concise. Additionally, the warning message is
now logged when osd_id is None or 'null', ensuring consistency in
error handling.
Also, this fixes the unit test `api/test_lvm.py::TestVolume::test_is_not_ceph_device()`
as `api.lvm.is_ceph_device()` expects a `Volume` object.

Signed-off-by: Guillaume Abrioux <gabrioux@ibm.com>