test: add prominent message in test script cleanup functions

When a test script fails in CI, it's often difficult to pinpoint the
exact line in the log where the script failed and the cleanup() function
(trapped on EXIT) begins.

Adding a prominent line (with greenprint where available) at the start
of the cleanup function will make reading logs of failed jobs a lot
easier.

test/cases/azure.sh

@@ -47,6 +47,7 @@ fi
 
 TEMPDIR=$(mktemp -d)
 function cleanup() {
+    greenprint "== Script execution stopped or finished - Cleaning up =="
     sudo rm -rf "$TEMPDIR"
 }
 trap cleanup EXIT