TEST-74-AUX-UTILS: Use tee

Something is failing but we can't see what from the logs so let's use
tee so we can.

test/units/TEST-74-AUX-UTILS.machine-id-setup.sh

@@ -71,7 +71,7 @@ testcase_transient() {
 
 # Check if we correctly processed the invalid machine ID we set up in the respective
 # test.sh file
-systemctl --state=failed --no-legend --no-pager >/failed
+systemctl --state=failed --no-legend --no-pager | tee /failed
 test ! -s /failed
 
 run_testcases