obexd: Fix file_op_complete callback

obexd: Fix file_op_complete callback

The file_op_complete callback added for the OBEX session command queuing
is called with a file_data parameter and not with a pending_request.

This fixes a crash when calling one of the file commands (like delete).

  0  0x0000000000438cd6 in file_op_complete (session=0x6a9d30,
       transfer=0x0,
     err=0x0, user_data=0x6762e0) at obexd/client/session.c:1054
  1  0x0000000000438c64 in async_cb (obex=0x6aa980, err=0x0,
       rsp=0x67a710,
     user_data=0x6ac2c0) at obexd/client/session.c:1035
  2  0x000000000041cbcc in handle_response (obex=0x6aa980, err=0x0,
     rsp=0x67a710) at gobex/gobex.c:949
  3  0x000000000041d49f in incoming_data (io=0x67d0f0, cond=G_IO_IN,
     user_data=0x6aa980) at gobex/gobex.c:1192
  4  0x00007ffff702de46 in g_main_context_dispatch ()
     from /usr/lib/libglib-2.0.so.0
  5  0x00007ffff702e198 in ?? () from /usr/lib/libglib-2.0.so.0
  6  0x00007ffff702e59a in g_main_loop_run () from
       /usr/lib/libglib-2.0.so.0
  7  0x00000000004309f0 in main (argc=1, argv=0x7fffffffddc8)
     at obexd/src/main.c:319