Update default logging for pgc_mosaic.py

[bakkerbakker]

Default slurm logging for pgc_ortho.py, pgc_pansharpen.py, and pgc_ndvi.py was updated in the PR here to output the slurm logs in the parent folder of the output directory, but pgc_mosaic.py handles logging slightly differently due to subtile processing, so those changes have not been added to pgc_mosaic.py yet.