Sentinel2 mpi mode processing bug > tmp file name collision

[samfranklin]

@petebunting, apologies it looks like I have accidentially reintroduced the "Temporary file collision" with my PR #13.

If you remember, back in Feb 2023, @CathyJinJNCC submitted a PR #11 to fix a bug where two threads when running in mpi mode, are processing two versions of the same Sentinel 2 tiles. Cathy fixed this my creating a unique tile and generation timestamp file name.

Somehow, I managed to revert these changes with my latest fix. I'm currently testing a new branch/PR and will submit when ready.

Thanks