qa: handle CEPH_CLI_TEST_DUP_COMMAND on ceph osd create

If CEPH_CLI_TEST_DUP_COMMAND is set when ceph osd create is called, it
will create two osd. They must be cleaned up afterwards instead of
assuming only one is going to be created.

http://tracker.ceph.com/issues/10083 Fixes: #10083

Signed-off-by: Loic Dachary <ldachary@redhat.com>