kbx: Fix error paths to fall back to D-lines.
* kbx/kbx-client-util.c (prepare_data_pipe): Return an error. (kbx_client_data_new): Recover from an error by use of D-lines. (kbx_client_data_release): Handle the case of use of D-lines.
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>