test-tool: add iSCSI SendTargets.Invalid test case

This test sends a series of Text request PDUs with key-value data that
doesn't match SendTargets=All.

Signed-off-by: David Disseldorp <ddiss@suse.de>

test-tool/iscsi-test-cu.h

@@ -79,6 +79,7 @@ void test_iscsi_cmdsn_toolow(void);
 
 void test_iscsi_datasn_invalid(void);
 void test_iscsi_sendtargets_simple(void);
+void test_iscsi_sendtargets_invalid(void);
 
 void test_mandatory_sbc(void);