Revert "filesetup: ensure that we align file starting offset"

Revert "filesetup: ensure that we align file starting offset"

There are valid reasons to use an offset that isn't a multiple
of the block size. We previously made this change to fix an
issue with a job file, but that job file had an offset that
wasn't a multiple of the hardware block size. As long as the
offset is a multiple of the hardware block size for unbuffered
IO, then it should be fine.

This reverts commit c465cd14ca958dfdb87bb1998add722d62ae3691.