Add unique folder name for add_file_template test

What does this MR do?

This is a follow-up to !36835 (merged), one more test needs a similar fix.

We need to make sure template files are created in unique-named folders, so that if the test fails after template creation and retries it doesn't get "The name x is already taken in this directory" error.

Closes #220997 (closed)

Does this MR meet the acceptance criteria?

Conformity

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