Seed random tensor generation so gpu tests are deterministic

**Description of changes:** **Related Issues:** Linked Issues: - Issue # Issues closed by this PR: - Closes # <!-- Reviewable:start --> - - - This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/flexflow/flexflow-train/1627) <!-- Reviewable:end -->