Update experiment dir to /tmp in CI tests

[cuichenx]

What does this PR do ?

Follow up PR to #10632. Change CI test experiment dir to /tmp

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[github-actions]

[🤖]: Hi @cuichenx 👋,

We wanted to let you know that a CICD pipeline for this PR just finished successfully

So it might be time to merge this PR or get some approvals

I'm just a bot so I'll leave it you what to do next.

//cc @pablo-garay @ko3n1g