TESTS: Add different log levels to the TUR test test suite and see how it looks

Add different log levels and update the TUR testsute.
Update the helper for testunitready() so that it
* prints FAILURE messages for normal and verbose levels
* prints selfdocumenting messages for which SCSI command it sends and the expected result for the verbose level

test-tool/iscsi-test.c

@@ -40,6 +40,7 @@
 #define discard_const(ptr) ((void *)((intptr_t)(ptr)))
 #endif
 
+int loglevel = LOG_VERBOSE;
 
 int (*real_iscsi_queue_pdu)(struct iscsi_context *iscsi, struct iscsi_pdu *pdu);