iscsi-command: fix unsolicited data-out length

the recent implementation allows to send
iscsi->first_burst_length + iscsi->target_max_recv_data_segment_length
bytes if immediate and unsolicited data-out is send and
iscsi->target_max_recv_data_segment_length < iscsi->first_burst_length.

RFC3720 defines the length as:

Length=(min(FirstBurstLength, Expected Data
   Transfer Length) - Received Immediate Data Length).

so that immediate data and unsolicited data-out are together
FirstBurstLength at maximum.

Signed-off-by: Peter Lieven <pl@kamp.de>

lib/iscsi-command.c

@@ -193,11 +193,8 @@ iscsi_timeout_scan(struct iscsi_context *iscsi)
 int
 iscsi_send_unsolicited_data_out(struct iscsi_context *iscsi, struct iscsi_pdu *pdu)
 {
-	uint32_t len = pdu->expxferlen - pdu->payload_len;
+	uint32_t len = MIN(pdu->expxferlen, iscsi->first_burst_length) - pdu->payload_len;
 
-	if (len > iscsi->first_burst_length) {
-		len = iscsi->first_burst_length;
-	}
 	return iscsi_send_data_out(iscsi, pdu, 0xffffffff,
 				   pdu->payload_len, len);
 }