TESTS: Create a test that tries to overflow the maxcmdsn counter

so that i/o from the initiator stops flowing and are just queued locally
until teh cmdsn window opens up again.

Send a lot of writes that block until we have processed the R2T
back from the target and verify we can still make process when we
have saturated the cmdsn window and are also blocked waiting for R2Ts.

test-tool/iscsi-test.c

@@ -245,6 +245,11 @@ struct scsi_test tests[] = {
 { "T1030_unsolicited_data_overflow",	T1030_unsolicited_data_overflow },
 { "T1031_unsolicited_data_out",		T1031_unsolicited_data_out },
 
+/* Test that if we start blocking new I/O due to saturating maxcmdsn
+   that we eventualld do recover and finish
+*/
+{ "T1040_saturate_maxcmdsn",		T1040_saturate_maxcmdsn },
+
 { NULL, NULL }
 };