sm: Use open_stream_nc for HANDLE by assuan_get_output_fd.
* sm/server.c (cmd_encrypt): Use gnupg_fd_t for OUT_FD. Call open_stream_nc with OUT_FD. (cmd_decrypt, cmd_verify, cmd_sign, cmd_export): Likewise.
- GnuPG-bug-id: T6580
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>