ceph-disk: cannot run unit tests

Because ceph-disk relies on hardcoded paths. The corresponding test will
be added back when ceph-disk can run from sources.

Fixes: #7085

Signed-off-by: Loic Dachary <loic@dachary.org>
(cherry picked from commit 2ba6930d62263a39f150ab43bf8cd860b9245188)