tests/ceph-disk: Let teardown clearing data

tests/ceph-disk: Let teardown clearing data

When running the ceph-disk check suite, 'test_mark_init' & 'test_activate_dir' had a
permission denied of the freshly created stuff like in :

tests/ceph-disk.sh:237: test_mark_init:  /bin/rm -fr /ceph/src/ceph-disk/test-ceph-disk/dir
/bin/rm: cannot remove « /ceph/src/ceph-disk/test-ceph-disk/dir/snap_1 »: Permission denied
/bin/rm: cannot remove « /ceph/src/ceph-disk/test-ceph-disk/dir/current »: Permission denied
/bin/rm: cannot remove « /ceph/src/ceph-disk/test-ceph-disk/dir/snap_2 »: Permission denied

Those two tests are starting a mon with run_mon.
Trying to delete the files while the daemon are still alive is impossible.
This patch removes the explicit 'rm' and let the teardown doing the cleaning
stuff by stopping daemons & cleaning content.

By using this patch, make check is now sucessful on ceph-disk.

Signed-off-by: Erwan Velu <erwan@redhat.com>