target: fix destroy device in target_configure_device

After dev->transport->configure_device succeeds, target_configure_device
exits abnormally, dev_flags has not set DF_CONFIGURED yet, does not call
destroy_device function in free_device.

Signed-off-by: tangwenji <tang.wenji@zte.com.cn>
Acked-by: Mike Christie <mchristi@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>