target: Fix write payload exception handling with ->new_cmd_map

This patch fixes a bug for fabrics using tfo->new_cmd_map() that
are expect transport_generic_request_failure() to be calling
transport_send_check_condition_and_sense() for both READ and WRITE,
instead of only for READ exceptions.

This was originally observed with a failed WRITE_SAME_16 w/ unmap=0
using tcm_loop.

Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>