TESTS: Add a new test that does a one block write using unsilicited immediate data

As part of the test also validate the PDU that libiscsi generates and verify that
1, the PDU we send has the F flag set
2, that datasegmentlength for the PDU is one block

test-tool/iscsi-test.c

@@ -250,6 +250,8 @@ struct scsi_test tests[] = {
 */
 { "T1040_saturate_maxcmdsn",		T1040_saturate_maxcmdsn },
 
+{ "T1041_unsolicited__immediate_data",	T1041_unsolicited_immediate_data },
+
 { NULL, NULL }
 };