Make ownership filter consistent between relink and rimport #32

As of #31, rimport walks directories to find files to publish with no regard for who owns the file. relink.py, on the other hand, still filters to just the owner. This is necessary, I think, because the rimport makes it so commands are run as the staging owner, and thus we would need special handling to check that ownership by the calling user is checked.

It may be acceptable to go either way on this: Both check ownership or neither does. It feels weird to have this obvious failure case possibly lead to situations where someone publishes someone else's file but then can't relink it, so I lean towards both checking.

To investigate: Is it even possible for one CSEG user to delete another's file in the input data dir? Yes. In fact, this is what rimport does when relinking! It's only a manual call of relink.py that skips files the user doesn't own.