cephfs: remove directory created in the ChangeDir test
cephfs: remove directory created in the ChangeDir test

The test function that exercises ChangeDir was creating a directory
and leaving it behind. Add some basic cleanup to the test to try
and avoid leaking stuff between test runs.

Signed-off-by: John Mulligan <eda8ad33169deab44f9fe65847f99e368da6c91b@redhat.com>

ceph/go-ceph,ceph/go-ceph,ceph/go-ceph